Fallibilism and verificationism
It is easy to obtain confirmations, or verifications, for nearly every theory — if we look for confirmations.
Confirmations should count only if they are the result of risky predictions; that is to say, if, unenlightened
by the theory in question, we should have expected an event which was incompatible with the theory —
an event which would have refuted the theory.
Every "good" scientific theory is a prohibition: it forbids certain things to happen. The more a theory
forbids, the better it is.
A theory which is not refutable by any conceivable event is non-scientific. Irrefutability is not a virtue of
a theory (as people often think) but a vice.
Every genuine test of a theory is an attempt to falsify it, or to refute it. Testability is falsifiability; but
there are degrees of testability: some theories are more testable, more exposed to refutation, than others;
they take, as it were, greater risks.
Confirming evidence should not count except when it is the result of a genuine test of the theory; and this
means that it can be presented as a serious but unsuccessful attempt to falsify the theory. (I now speak in
such cases of "corroborating evidence.")
Some genuinely testable theories, when found to be false, are still upheld by their admirers — for
example by introducing ad hoc some auxiliary assumption, or by reinterpreting the theory ad hoc in such
a way that it escapes refutation. Such a procedure is always possible, but it rescues the theory from
refutation only at the price of destroying, or at least lowering, its scientific status. (I later described such a
rescuing operation as a "conventionalist twist" or a "conventionalist stratagem.")
World 1 is the physical universe. It consists of the actual truth and reality that we try to represent,
such as energy, physics, and chemistry. While we exist in this world, we do not always perceive it
and then represent it correctly.
World 2 is the world of our subjective personal perceptions, experiences, and cognition. It is what we
think about the world as we try to map, represent, and anticipate or hypothesis in order to maintain
our existence in an every changing place. Personal knowledge and memory form this world, which
are based on self-regulation, cognition, consciousness, dispositions, and processes. Note that Polanyi's
theory of tacit and explicit knowledge is based entirely within this world.
World 3 is the sum total of the objective abstract products of the human mind. It consists of such
artifacts as books, tools, theories, models, libraries, computers, and networks. It is quite a diverse
mixture. While knowledge may be created and produced by World 2 activities, its artifacts are stored
in World 3, for example a claw-hammer, Maslow's hierarchy of needs, and Godel's proof of the
incompleteness of arithmetic. Popper also includes genetic heredity (if you think about it, genes are
really nothing more than a biological artifact of instructions).
Karl Popper, who died in 1994, was widely regarded as England's greatest philosopher of science since
Bertrand Russell. Indeed a philosopher of worldwide eminence. Today his followers among philosophers
of science are a diminishing minority, convinced that Popper's vast reputation is enormously inflated. I
1
agree. I believe that Popper's reputation was based mainly on this persistent but misguided efforts to
restate common-sense views in a novel language that is rapidly becoming out of fashion. Consider
Popper's best known claim: that science does not proceed by "induction"—that is, by finding confirming
instances of a conjecture — but rather by falsifying bold, risky conjectures. Conformation, he argued, is
slow and never certain. By contrast, a falsification can be sudden and definitive. Moreover, it lies at the
heart of the scientific method.
A familiar example of falsification concerns the assertion that all crows are black. Every find of another
black crow obviously confirms the theory, but there is always the possibility that a non-black crow will
turn up. If this happens, the conjecture is instantly discredited. The more often a conjecture passes efforts
to falsify it, Popper maintained, the greater becomes its "corroboration," although corroboration is also
uncertain and can never be quantified by degree of probability. Popper's critics insist that "corroboration"
is a form of induction, and Popper has simply sneaked induction in through a back door by giving it a
new name. David Hume's famous question was "How can induction be justified?" It can't be, said Popper,
because there is no such thing as induction!
There are many objections to this startling claim. One is that falsifications are much rarer in science than
searches for confirming instances. Astronomers look for signs of water on Mars. They do not think they
are making efforts to falsify the conjecture that Mars never had water.
Falsifications can be as fuzzy and elusive as confirmations. Einstein's first cosmological model was a
universe as static and unchanging as Aristotle's. Unfortunately, the gravity of suns would make such a
universe unstable. It would collapse. To prevent this, Einstein, out of thin air, proposed the bold
conjecture that the universe, on its pre-atomic level, harbored a mysterious, undetected repulsive force he
called the "cosmological constant." When it was discovered that the universe is expanding, Einstein
considered his conjecture falsified. Indeed, he called it "the greatest blunder of my life." Today, his
conjecture is back in favor as a way of explaining why the universe seems to be expanding faster than it
should. Astronomers are not trying to falsify it; they are looking for confirmations.
Falsification may be based on faulty observation. A man who claims he saw a white crow could be
mistaken or even lying. As long as observation of black crows continue, it can be taken in two ways; as
confirmations of "all crows are black," or disconfirmations of "some crows are not black." Popper
recognized — but dismissed as unimportant — that every falsification of a conjecture is simultaneously a
confirmation of an opposite conjecture, and every conforming instance of a conjecture is a falsification of
an opposite conjecture.
Consider the current hypothesis that there is a quantum field called the
Higgs field, with its quantized particle. If a giant atom smasher some
day, perhaps soon, detects a Higgs, it will confirm the conjecture that the
field exist. At the same time it will falsify the opinion of some top
physicists, Oxford's Roger Penrose for one, that there is no Higgs field.
To scientists and philosophers outside the Popperian fold, science
operates mainly by induction (confirmation), and also and less often by
disconfirmation (falsification). Its language is almost always one of
induction. If Popper bet on a certain horse to win a race, and the horse
won, you would not expect him to shout, "Great! My horse failed to
lose!"
Astronomers are now finding compelling evidence that smaller and smaller planets orbit distant suns.
Surely this is inductive evidence that there may be Earth-sized planets out there. Why bother to say, as
each new and smaller planet is discovered, that it tends to falsify the conjecture that there are no small
planets beyond our solar system? Why scratch your left ear with your right hand? Astronomers are
looking for small planets. They are not trying to refute a theory any more than physicists are trying to
refute the conjecture that there is no Higgs field. Scientists seldom attempt to falsify. They are
inductivists who seek positive conformations.
At the moment the widest of all speculations in physics is superstring theory. It conjectures that
all basic particles are different vibrations of extremely tiny loops of great tensile strength. No
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superstring has yet been observed, but the theory has great explanatory power. Gravity, for
example, is implied as the simplest vibration of a superstring. Like prediction, explanation is an
important aspect of induction. Relativity, for instance, not only made rafts of successful
predictions but explained data previously unexplained. The same is true of quantum mechanics.
In both fields researchers used classical induction procedures. Few physicists say they are
looking for ways to falsify superstring theory. They are instead looking for confirmations. Ernest
Nagel, Columbia University's famous philosopher of science, in his Teleology Revisited and
Other Essays in the Philosophy and History of Science (1979), summed it up this way:
"[Popper's] conception of the role of falsification . . . is an oversimplification that is close to
being a caricature of scientific procedures."
For Popper, what his chief rival Rudolf Carnap called a "degree of confirmation"—a logical relation
between a conjecture and all relevant evidence—is a useless concept. Instead, as I said earlier, the more
tests for falsification a theory passes, the more it gains in "corroboration." It's as if someone claimed that
deduction doesn't exist, but of course statements can logically imply other statements. Let's invent a new
term for deduction, such as "justified inference." It's not so much that Popper disagreed with Carnap and
other inductivists as that he restated their views in a bizarre and cumbersome terminology.
To Popper's credit he was, like Russell, and almost all philosophers, scientists, and ordinary people, a
thoroughgoing realist in the sense that he believed the universe, with all its intricate and beautiful
mathematical structures, was "out there," independent of our feeble minds, In no way can the laws of
science be likened to traffic regulations or fashions in dress that very with time and place. Popper would
have been appalled as Russell by the crazy views of today's social constructivists and postmodernists,
most of them French or American professors of literature who know almost nothing about science.
Scholars unacquainted with the history of philosophy often credit popper for being the first to point out
that science, unlike math and logic, is never absolutely certain. It is always corrigible, subject to perpetual
modification. This notion of what the American philosopher Charles Peirce called the "fallibilism" of
science goes back to ancient Greek skeptics, and is taken for granted by almost all later thinkers.
In Quantum Theory and the Schism in Physics (1982) Popper defends at length his "propensity theory" of
probability. A perfect die, when tossed, has the propensity to show each face with equal probability. Basic
particles, when measured, have a propensity to acquire, with specific probabilities, such properties as
position, momentum, spin and so on. Here again Popper is introducing a new term which says nothing
different from what can be better said in conventional terminology.
In my opinion Popper's most impressive work, certainly his best known, was his two-volume The Open
Society and Its Enemies (1945). Its central theme, that open democratic societies are far superior to closed
totalitarian regimes, especially Marxist ones, was hardly new, but Popper defends it with powerful
arguments and awesome erudition. In later books he attacks what he calls "historicism," the belief that
there are laws of historical change that enable one to predict humanity's future. The future is
unpredictable, Popper argued, because we have free wills. Like William James, Popper was an
indeterminist who saw history as a series of unforeseeable events. In later years he liked to distinguish
between what he called three "worlds"—the external physical universe, the inner world of the mind, and
the world of culture. Like Carnap and other members of the Vienna Circle, he had no use for God or an
afterlife.
I am convinced that Popper, a man of enormous egotism, was motivated by an intense jealousy of Carnap.
It seems that every time Carnap expressed an opinion, Popper felt compelled to come forth with an
opposing view, although it usually turned out to be the same as Carnap's but in different language. Carnap
once said that the distance between him and Popper was not symmetrical. From Carnap to Popper it was
small, but the other way around it appeared huge. Popper actually believed that the movement known as
logical positivism, of which Carnap was leader, had expired because he, Popper, had single-handedly
killed it!
Popper's great and tireless efforts to expunge the word induction from scientific and
philosophical discourse has utterly failed. Except for a small but noisy group of British
Popperians, induction is just too firmly embedded in the way philosophers of science and even
ordinary people talk and think.
3
Confirming instances underlie our beliefs that the Sun will rise tomorrow, that dropped objects
will fall, that water will freeze and boil, and a million other events. It is hard to think of another
philosophical battle so decisively lost.
Bold ideas, unjustified anticipations, and speculative thought are our only means for interpreting nature:
our only organon, our only instrument for grasping her. And we must hazard them to win our prize.
Those among us who are unwilling to expose their ideas to the hazard of refutation do not take part in the
scientific game. (From "The Logic of Scientific Discovery)
Popper described his philosophy as critical rationalism, indicating his rejection of classical empiricism,
and the observationalist-inductivist account of science that had grown from it. In his most influential
book, the Logic of Scientific Discovery, he argued that scientific theories are universal, but can be tested
only by the predictions that arise from them. He argued that scientific theory (and human knowledge
generally) is always conjectural, generated by imagination to solve problems that arise in particular
historico-cultural settings. No number of positive outcomes of experimental tests can prove that a
scientific theory is true, but just one counterexample is enough to prove it false. This logical asymmetry
between verification and falsification is at the heart of his philosophy of science, and it led him to make
falsifiability his criterion of demarcation between what is and is not scientific: a theory should be
considered scientific if and only if it is falsifiable.
Popper thus attacked psychoanalysis and Marxism on the grounds that their explanations are not
falsifiable. He also argued against the Copenhagen interpretation of quantum mechanics. He disagreed
with Niels Bohr's instrumentalism and supported Albert Einstein's realist approach to scientific theories
about the universe. Popper's falsificationism resembles Charles Peirce's fallibilism. In Of Clocks and
Clouds (1966), Popper said he wished he had known of Peirce's work earlier.
In All Life is Problem Solving, Popper tried to explain why our understanding of the universe seems to
improve over time. If our theories can never be proved scientifically, how is it that the growth of science
results in a growth in knowledge? In his view, the advance of scientific knowledge is an evolutionary
process characterised by:
In response to a given problem (
), several competing theories (
attempts at falsification. This process, error elimination (
), are subjected to rigorous
), performs for science what natural
selection performs for evolution. Theories that better survive the process are not more true, but rather,
more "fit"—' more applicable to the problem situation at hand (
). Consequently, just as a species'
"biological fit" does not predict continued survival, no amount of testing however rigorous can guarantee
that a scientific theory will not be disproved in the future. Yet, just as biological evolution has produced,
over time, adaptive traits equipped to deal with more and more complex problems of survival, similarly,
the evolution of theories through the scientific method may reflect progress toward more interesting
problems (
). For Popper, it is in the interplay between the tentative theories (conjectures) and error
elimination (refutation) that scientific knowledge advances; in a process very much akin to the interplay
between genetic variation and natural selection.
Where does "truth" fit into this? In 1934 Popper wrote of the search for truth as one of the "strongest
motives for scientific discovery". Still, he describes in Objective Knowledge (1972) concerns about the
4
notion of truth as correspondence. Then came the semantic theory of truth formulated by the logician
Alfred Tarski. Popper writes of learning in 1935 about the consequences of Tarski's theory, to his intense
joy. The theory met critical objections to truth as correspondence and also seemed to Popper to support
metaphysical realism and the regulative idea of a search for truth.
According to this theory, both the conditions for the truth of a sentence, and the sentences themselves, are
part of a metalanguage. For example, the sentence "Snow is white" is true if and only if snow is white.
Popper refers to it as a theory in which "is true" is replaced with "corresponds to the facts". He bases this
on examples such as the one described above which refer to two things: assertions and the facts to which
they refer. He identifies Tarski's formulation of the truth conditions of sentences as the introduction of a
"metalinguistic predicate" and distinguishes between: "John called" is true, and "It is true that John
called." The former belongs to the metalanguage while the latter is more likely to belong to the object
language. Hence, "it is true that" has the logical status of a redundancy, while "Is true" is a predicate
necessary for general observations such as "John was telling the truth about Phillip."
Popper went on to develop his notion of verisimilitude. The idea behind this is that scientific assertions
can be measured by the amount of truth and falsity that they imply. In this way, one theory can be
evaluated as more or less true than another on a quantitative basis which has nothing to do with
"subjective probabilities" or other merely "epistemic" considerations.
The simplest mathematical formulation that Popper gives of this is in the tenth chapter of Conjectures and
Refutations, where he defines it as:
where
is the verisimilitude (or truthlikeness) of a,
and
measures the content of the falsity of a.
measures the content of truth of a,
Knowledge, for Popper, was objective in that it is objectively true (or truthlike), and also in that
knowledge has an ontological status (i.e., knowledge as object) independent of the knowing subject
(Objective Knowledge: An Evolutionary Approach, 1972). He proposed three worlds:
World One, the phenomenal world, of direct experience;
World Two, the world of mind, or mental states, ideas, and perceptions; and
World Three, human knowledge expressed in all its forms, or the products of the second world made
manifest in the materials of the first (–books, papers, paintings, symphonies, and all the products of the
mind).
The influence of World Three, in his view, on World Two is at least as strong as the influence of World
One. In other words, the knowledge in an individual mind owes at least as much to the accumulated
wealth of human knowledge as to direct experience. As such, the growth of knowledge could be said to
be a function of the independent evolution of World Three. Many contemporary philosophers have not
embraced Popper's Three World conjecture, due mostly to its resemblance to Cartesian dualism.
5
In The Open Society and Its Enemies and The Poverty of Historicism, Popper developed a critique of
historicism and a defence of the 'Open Society' and liberal democracy. For Popper, the major question of
political philosophy is not “Who should rule?”, but “How can we get rid of bad rulers?”. He saw
democracy as the best answer to the second question, not the first, but if we are to get rid of unsatisfactory
rulers through democratic processes, we must be able to criticize them, and that requires an open society.
Historicism, as Popper used the term, is the theory that history progresses by general laws towards a
determinate end[2] Popper argued that this view underpins most forms of authoritarianism and
totalitarianism, and that it is based on mistaken assumptions about the nature of scientific law and
prediction. Because the evolution of human history depends on the growth of human knowledge, and
because no society can predict its own future states of knowledge, he argued that it is not possible to
make a predictive science from the study of human history.
Among his contributions to philosophy is his answer to David Hume's Problem of Induction. According
to Hume, just because the sun has risen every day for as long as anyone can remember, there is no
rational reason to believe it will rise again tomorrow. There way to be sure that a pattern will continue on
just because it has before. Popper's reply is that although we cannot prove that the sun will come up, we
can theorize that it will. If it does not come up, then it will be disproven, but until the theory is disproven
we can accept it. Thus, Popper's demarcation between science and non-science serves as an answer to an
old logical problem as well. This approach was criticised by Peter Singer for masking the role induction
plays in empirical discovery.
Popper played a vital role in establishing the philosophy of science as an autonomous discipline within
analytic philosophy. In 1946, he founded the Department of Philosophy, Logic and Scientific Method at
the London School of Economics, where he influenced Imre Lakatos and Paul Feyerabend, two important
philosophers of science in the next generation of analytic philosophy.
Popper had a long and close friendship with economist Friedrich Hayek, who also came to the London
School of Economics from Vienna. In a letter to Hayek in 1944, Popper wrote, "I think I have learnt more
from you than from any other living thinker, except perhaps Alfred Tarski." (See Hacohen, 2000). Popper
dedicated his Conjectures and Refutations to Hayek. For his part, Hayek dedicated a collection of papers,
Studies in Philosophy, Politics, and Economics, to Popper, and in 1982 said, "...ever since his Logik der
Forschung first came out in 1934, I have been a complete adherent to his general theory of methodology.".
Popper also had long and influential friendships with art historian Ernst Gombrich, biologist Peter
Medawar, and neuroscientist John Carew Eccles.
Among Popper's students at the London School of Economics was George Soros, who said that his
investment strategies are modelled on Popper's understanding of the advancement of knowledge through
falsification. Among Soros's philanthropic foundations is the Open Society Institute, a think-tank named
in honour of Popper's The Open Society and Its Enemies, which Soros founded to advance the defense of
the open society against authoritarianism and totalitarianism.
The Quine-Duhem thesis argues that it is impossible to test a single hypothesis on its own, since each one
comes as part of an environment of theories. Thus we can only say that the whole package of relevant
theories has been collectively falsified, but cannot conclusively say which element of the package must be
6
replaced. An example of this is given by the discovery of the planet Neptune: when the motion of the
planet Uranus was found not to match the predictions of Newton's laws, the theory "there are seven
planets in the solar system" was rejected, and not Newton's laws themselves. Popper discussed this
critique of naïve falsificationism in chapters three and four of The Logic of Scientific Discovery. For
Popper, theories are accepted or rejected via a sort of “natural selection.” Theories that say more about the
way things appear are to be preferred over those that do not; the more generally applicable a theory is, the
greater its value. Thus Newton’s laws, with their wide general application, are to be preferred over the
much more specific “the solar system has seven planets.”
Thomas Kuhn’s influential book The Structure of Scientific Revolutions argued that scientists work in a
series of paradigms, and found little evidence of scientists actually following a falsificationist
methodology. Although Kuhn does not put it in these terms, there is an implicit rejection in Kuhn's work
of the old positivist "context of discovery" vs. "context of justification" distinction because Kuhn sees
discovery and justification as going together (although he does not speak of justification in the way that
the positivists did). But Popper clung to this distinction, saying that the process of coming up with a new
theory is extra-logical, and only the process of falsification of that theory follows a logical procedure.
Popper's student Imre Lakatos attempted to reconcile Kuhn’s work with falsificationism by arguing that
science progresses by the falsification of research programs rather than the more specific universal
statements of naïve falsificationism. Another of Popper’s students, Paul Feyerabend, ultimately rejected
any prescriptive methodology, and argued that the only universal method characterizing scientific
progress was anything goes.
Popper seems to have anticipated Kuhn's observations. In his collection Conjectures and Refutations: The
Growth of Scientific Knowledge (Harper & Row, 1963), Popper writes:
[S]cience must begin with myths, and with the criticism of myths; neither with the collection of
observations, nor with the invention of experiments, but with the critical discussion of myths, and of
magical techniques and practices. The scientific tradition is distinguished from the pre-scientific tradition
in having two layers. Like the latter, it passes on its theories; but it also passes on a critical attitude
towards them. The theories are passed on, not as dogmas, but rather with the challenge to discuss them
and improve upon them.
Another objection is that it is not always possible to demonstrate falsehood definitively, especially if one
is using statistical criteria to evaluate a null hypothesis. More generally, it is not always clear that if
evidence contradicts a hypothesis that this is a sign of flaws in the hypothesis rather than of flaws in the
evidence. However, this is a misunderstanding of what Popper's philosophy of science sets out to do.
Rather than proffering a set of instructions that merely need to be followed diligently to achieve science,
Popper makes clear in The Logic of Scientific Discovery, his belief that the resolution of conflicts between
hypotheses and observations can only be a matter of the judgment of scientists, in each individual case.
Other critics seek to vindicate the claims of historicism or holism to intellectual respectability, or
psychoanalysis or Marxism to scientific status. It has been argued that Popper's student Imre Lakatos
transformed Popper's philosophy using historicist and updated Hegelian historiographic ideas.
Charles Taylor accuses Popper of exploiting his fame as an epistemologist to diminish the importance of
philosophers of the continental tradition. According to Taylor, Popper's criticisms are completely baseless,
but they are received with an attention and respect that Popper's "intrinsic worth hardly merits."
Martin Gardner allegedly claimed Popper had "enormous egotism," and was motivated by an "intense
jealousy of Rudolf Carnap."
A. A. Derksen examined the development of Popper's thought from The Logic of Scientific Discovery,
through Conjectures and Refutations (1963) to Objective Knowledge (1972), and concluded that, instead
of having a unified deductive system, "we are left with a disconnected theory, its parts in need of
support." Falsifiability, according to Derksen, is not one thing, but several. Derksen's final conclusion is
that Popper's deductivist system cannot stand, and that what emerges is a form of inductivism.
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In 2004, philosopher and psychologist Michel ter Hark of Groningen, Netherlands, published a book,
Popper, Otto Selz and the Rise of Evolutionary Epistemology, in which he claims that Popper got part of
his ideas from his tutor, the German-Jewish psychologist Otto Selz. Selz himself never published his
ideas, partly because of the rise of Nazism which forced him to quit his work in 1933, and the prohibition
of referencing to Selz' work.
The Vienna Circle was a group of early twentieth-century philosophers who sought to reconceptualize
empiricism by means of their interpretation of then recent advances in the physical and formal sciences.
Their radically anti-metaphysical stance was supported by an empiricist criterion of meaning and a
broadly logicist conception of mathematics. They denied that any principle or claim was synthetic a
priori. Moreover, they sought to account for the presuppositions of scientific theories by regimenting
such theories within a logical framework so that the important role played by conventions, either in the
form of definitions or of other analytical framework principles, became evident. The Vienna Circle's
theories were constantly changing. In spite (or perhaps because) of this, they helped to provide the
blueprint for analytical philosophy of science as meta-theory—a “second-order” reflection of “first-order”
sciences. While the Vienna Circle's early form of logical empiricism (or logical positivism or
neopositivism: these labels will be used interchangably here) no longer represents an active research
program, recent history of philosophy of science has unearthed much previously neglected variety and
depth in the doctrines of the Circle's protagonists, some of whose positions retain relevance for
contemporary analytical philosophy.
While it is in the nature of philosophical movements and their leading doctrines to court controversy, the
Vienna Circle and its philosophies did so more than most. To begin with, its members styled themselves
as conceptual revolutionaries who cleared the stables of academic philosophy by showing metaphysics
not simply to be false, but to be cognitively empty and meaningless. In addition, they often associated
their attempt to overcome metaphysics with their public engagement for scientific Enlightenment reason
in the ever-darkening political situation of 1920s and 1930s central Europe. Small wonder then that the
Vienna Circle has sharply divided opinion from the start. There is very little beyond the basic facts of
membership and its record of publications and conferences that can be asserted about it without courting
some degree of controversy. Two facts must be clearly recognized if a proper evaluation of the Vienna
Circle is to be attempted. The first is, that, despite its relatively short existence, even some of the most
central theses of the Vienna Circle underwent radical changes. The second is that its members were by no
means of one mind in all important matters; occasionally they espoused perspectives so radically at
variance with each other that even their ostensive agreements cannot remain wholly unquestioned. Behind
the rather thin public front, then, quite different philosophical projects were being pursued by the leading
participants with, moreover, changing alliances. One way of taking account of this is by speaking (as
above) explicitly of the philosophies (in the plural) of the Vienna Circle (and to avoid the singular definite
description) while using the expression “Vienna Circle philosophy” (without an article) in a neutral
generic sense.
Recent scholarship has provided what the received view of Viennese neopositivism lacks: recognition and
documentation of the sometimes sharply differentiated positions behind the generic surface. This does not
invalidate all previous scholarship, including some fundamental criticisms of its positions, but it restores a
depth to Vienna Circle philosophy that was absent from the standard histories. The value of this
development must not be underestimated, for the recognition of the Vienna Circle's sophisticated
engagement with aspects of the philosophical tradition and contemporaneous challenges calls into
question unwarranted certainties of our own self-consciously post-positivist era. While there remains
support for the view that philosophical doctrines were held in the Vienna Circle that wholly merited many
of the standard criticisms to be cited below, there is now also support for the view that in nearly all such
cases, these doctrines were already in their day opposed within the Circle itself. While some of the
Vienna Circle philosophies are dated and may even be, as John Passmore once put it, as dead as
philosophies can be, others show signs of suprising virulence. Which ones these are, however, remains
controversial.
The lead pursued in this article is provided by the comments of a long-time associate of the Vienna Circle,
C.G. Hempel, made in 1991: “When people these days talk about logical positivism or the Vienna Circle
and say that its ideas are passé, this is just wrong. This overlooks the fact that there were two quite
different schools of logical empiricism, namely the one of Carnap and Schlick and so on and then the
quite different one of Otto Neurath, who advocates a completely pragmatic conception of the philosophy
of science…. And this form of empiricism is in no way affected by any of the fundamental objections
8
against logical positivism…” (Quoted in Wolters 2003, 117). Without setting out to endorse Hempel's
specific claim, the aim here is to fill out his suggestive picture by indicating what Schlick, Carnap and
Neurath stand for philosophically and why the different wings of the Vienna Circle require differentiated
assessments. After reviewing the basic facts and providing an overall outline of Vienna Circle philosophy
(in sect. 2), this article considers various doctrines in greater detail by way of discussing standard
criticisms with the appropriate distinctions in mind (in sect. 3). No comprehensive assessment of the
Vienna Circle and the work of its members can be attempted here, but some basic conclusions will be
drawn (in sect. 4).
The Vienna Circle was a group of scientifically trained philosophers and philosophically interested
scientists who met under the (nominal) leadership of Moritz Schlick for often weekly discussions of
problems in the philosophy of science during academic terms in the years from 1924 to 1936. As is not
uncommon with such groups, its identity is blurred along several edges. Not all of those who ever
attended the discussions can be called members, and not all who attended did so over the entire period.
Typically, attention is focused on long-term regulars who gained prominence through their philosophical
publications, but even these do not in all cases fall into the period of the Vienna Circle proper. It is natural,
nevertheless, to consider under the heading “Vienna Circle” also the later work of leading members who
were still active in the 1940s, 50s and 60s. Finally, there is the so-called periphery of international
contacts and visitors that prefigured the post-World War II network of analytical philosophers of science.
In the present article the emphasis will be placed on the long-term regulars whose contributions will be
followed, selectively, into the post-Schlick era.
According to its unofficial manifesto (see section 2.3 below), the Circle had “members” and recognized
others as “sympathetic” to its aims. It included as members, besides Schlick who had been appointed to
Mach's and Boltzmann's old chair in Philosophy of the Inductive Sciences at the University of Vienna in
1922, the mathematician Hans Hahn, the Prague physicist Philipp Frank, the social scientist Otto Neurath,
his wife, the mathematician Olga Hahn-Neurath, the philosopher Viktor Kraft, the mathematicians
Theodor Radacovic and Gustav Bergmann and, since 1926, the philosopher and logician Rudolf Carnap.
(Even before World War I, there existed a similarly oriented discussion circle that included Frank, Hahn
and Neurath. During the time of the Schlick Circle, Frank resided in Prague throughout, Carnap did so
from 1931.) Further members were recruited among Schlick's students, like Friedrich Waismann, Herbert
Feigl and Marcel Natkin, others were recruited among Hahn's students, like Karl Menger and Kurt Gödel.
Though listed as members in the manifesto, Menger and Kraft later wanted to be known only as as
sympathetic associates, like, all along, the mathematician Kurt Reidemeister and the philosopher and
historian of science Edgar Zilsel. (Karl Popper was never a member or associate of the Circle, though he
studied with Hahn in the 1920s and in the early 1930s discussed its doctrines with Feigl and Carnap.)
Over the years, other participants (not listed in the manifesto) included other students of Schlick's and
Hahn's like Bela von Juhos, Josef Schächter, Walter Hollitscher, Heinrich Neider, Rose Rand, Josef
Rauscher and Käthe Steinhardt, a secondary teacher, Robert Neumann, and, as notable thinkers with
independent connections, the jurist and philosopher Felix Kaufmann (also a member of F.A. von Hayek's
“Geistkreis”) and the innovative psychologist Egon Brunswik (coming, like the even more loosely
associated sociologists Paul Lazarsfeld and Marie Jahoda, from the pioneering Karl Bühler's University
Institute of Psychology).
Despite its prominent position in the rich, if fragile, intellectual culture of inter-war Vienna and most
likely due to its radical doctrines, the Vienna Circle found itself virtually isolated in most of German
speaking philosophy. The one exception was its contact and cooperation with the Berlin Society for
Empirical (later: Scientific) Philosophy (the other point of origin of logical empiricism). The members of
the Berlin Society sported a broadly similar outlook and included, besides the philosopher Hans
Reichenbach, the logicians Kurt Grelling and Walter Dubislav, the psychologist Kurt Lewin, the surgeon
Friedrich Kraus and the mathematician Richard von Mises. (Its leading members Reichenbach, Grelling
and Dubislav were listed in the Circle's manifesto as sympathisers.) At the same time, members of the
Vienna Circle also engaged directly, if selectively, with the Warsaw logicians (Tarski visited Vienna in
1930, Carnap later that year visited Warsaw and Tarski returned to Vienna in 1935). Probably partly
because of its firebrand reputation, the Circle attracted also a series of visiting younger researchers and
students including Carl Gustav Hempel from Berlin, Hasso Härlen from Stuttgart, Ludovico Geymonat
from Italy, Jørgen Jørgensen, Eino Kaila, Arne Naess and Ake Petzall from Scandinavia, A.J. Ayer from
the UK, Albert Blumberg, Charles Morris, Ernest Nagel and W.V.O. Quine from the USA, H.A.
Lindemann from Argentina and Tscha Hung from China. (The reports and recollections of these former
visitors—e.g. Nagel 1936—are of interest in complementing the Circle's in-house histories and
9
recollections which start with the manifesto—Carnap, Hahn and Neurath 1929—and extend through
Neurath 1936, Frank 1941, 1949a and Feigl 1943 to the memoirs by Carnap 1963, Feigl 1969a, 1969b
and Bergmann 1987.)
The aforementioned social and political engagement of members of the Vienna Circle and of Vienna
Circle philosophy for Enlightenment reason had never made the advancement of its associates or
protegées easy in Viennese academia. From 1934 onwards, with anti-semitism institutionalized and
irrationalism increasingly dominating public discourse, this engagement began to cost the Circle still
more dearly. Not only was the Verein Ernst Mach closed down early that year for political reasons, but
the ongoing dispersal of Circle members by emigration, forced exile and death meant that after the
murder of Schlick in 1936 only a small rump was able to continue meetings for another two years in
Vienna. (1931: Feigl emigrated to USA; 1934: Hahn died, Neurath fled to Holland, 1940 to UK; 1935
Carnap emigrated to USA; 1936: Schlick murdered; 1937: Menger emigrated to USA, Waismann to UK;
1938: Frank, Kaufmann, Brunswik, Bergmann emigrated to USA; Zilsel, Rand to UK, later to USA;
Hollitscher fled to Switzerland, later to UK; Schächter emigrated to Palestine; 1940: Gödel emigrated to
USA; see Dahms 1995 for a chronology of the exodus.) But the end of the Vienna Circle as such did not
mean the end of its influence due to the continuing development of the philosophy of former members.
Particularly through their work in American exile (esp. Carnap at Harvard, Chicago and UCLA; Feigl at
Iowa and Minnesota; less so Frank at Harvard) and that of earlier American visitors (esp. Quine, Nagel),
as well as through the work of fellow emigrées from the Berlin Society (esp. Reichenbach, Hempel) and
their students (Hilary Putnam, Wesley Salmon), logical empiricism strongly influenced the post-World
War II development of analytic philosophy of science. By contrast, Waismann had little influence in the
UK where Neurath, already marginalized, had died in 1945. (The full story of logical empiricism's
acculturation in the English speaking world remains to be written, but see Howard 2003, Reisch 2005 and
Uebel 2005 for considerations of aspects of Vienna Circle philosophy that were neglected in the process
and remained long forgotten.)
After its formative phase which was confined to the Thursday evening discussions, the Circle went public
in 1928 and 1929 when it seemed that the time had come for their emerging philosophy to play a
distinctive role not only in the academic but also the public sphere. In November 1928, at its founding
session, Schlick accepted the presidency of the newly formed Verein Ernst Mach (Association Ernst
Mach), Hahn accepted one of its vice-presidencies and Neurath and Carnap joined its secretariat.
Originally proposed by the Austrian Freidenkerbund (Free Thinker Association), the Verein Ernst Mach
was dedicated to the dissemination of scientific ways of thought and so provided a forum for popular
lectures on the new scientific philosophy. In the following year the Circle stepped out under its own name
(invented by Neurath) with a manifesto and a special conference. The publication of “The Scientific
World Conception: The Vienna Circle”, signed by Carnap, Hahn and Neurath and dedicated to Schlick
(who was not wholly pleased by it), coincided with the “First Conference for the Epistemology of the
Exact Sciences” in mid-September 1929, organised jointly with the Berlin Society as an adjunct to the
Fifth Congress of German Physicists and Mathematicians in Prague (where Frank played a prominent role
in the local organising committee). A distinct philosophical school appeared to be emerging, one that was
dedicated to ending the previous disputes of philosophical schools by dismissing them, controversially, as
strictly speaking meaningless.
Throughout the early and mid-1930s the Circle kept a high and increasingly international profile with its
numerous publications and conferences. In 1930, the Circle took over, again together with the Berlin
Society, the journal Annalen der Philosophie and restarted it under the name of Erkenntnis with Carnap
and Reichenbach as co-editors. (Besides publishing original articles and sustaining lengthy debates, this
journal featured selected proceedings of their early conferences and documented the lecture series of the
Verein Ernst Mach and the Berlin Society as well as their international congresses.) Meanwhile, from
1928 until 1936, Schlick and Frank served as editors of their book series “Schriften zur
wissenschaftlichen Weltauffassung” (“Writings on the Scientific World Conception”), which published
major works by leading members and early critics like Karl Popper, while Neurath served, from 1933
until 1939, as editor of the series “Einheitswissenschaft” (“Unified Science”), which published more
introductory essays by leading members and sympathisers. Conference-wise, the Circle organized, again
with the Berlin Society, a “Second Conference for the Epistemology of the Exact Sciences” as an adjunct
to the Sixth Congress of German Physicists and Mathematicians in Königsberg in September 1930 (where
Reidemeister played a prominent role in the organisation) and then began the series of International
Congresses on the Unity of Science with a “Pre-Conference” just prior to the start of the Eighth
International Congress of Philosophy in Prague in September 1934. This, their last conference in Central
10
Europe, was followed by the International Congresses of various sizes in Paris (September 1935, July
1937), Copenhagen (June 1936), Cambridge, England (July 1938), Cambridge, Mass. (September 1939),
all in the main organized by Neurath; a smaller last gathering was held in Chicago in September 1941. By
1938 their collective publication activity began to centre on a monumentally planned International
Encyclopedia of Unified Science, with Neurath as editor-in-chief and Carnap and Charles Morris as coeditors; by the time of Neurath's death in 1945, only 10 monographs had appeared and the series was
wound up in 1970 numbering 20 monographs under the title “Foundations of the Unity of Science”
(notoriously containing Thomas Kuhn's Structure of Scientific Revolutions amongst them).
Individually, the members of the Vienna Circle published extensively before, during and after the years of
the Circle around Schlick. For some (Frank, Hahn, Menger, Neurath), philosophy was only part of their
scientific output, with numerous monographs and articles in their respective disciplines (mathematics,
physics and social science); others (Schlick, Carnap, Feigl, Waismann) concentrated on philosophy, but
even their output cared relatively little for traditional concerns of the field. Here it must be noted that two
early monographs by Schlick (1918/25) and Carnap (1928a), commonly associated with the Vienna
Circle, mostly predate their authors' participation there and exhibit a variety of influences not typically
associated with logical positivism. Moreover, important monographs by Frank (1932), Neurath (1931a),
Carnap (1934/37) and Menger (1934) in the first half of the 1930s represent moves away from positions
that had been held in the Circle before and contradict its orthodox profile. Yet the Circle's orthodoxy, as it
were, is not easily pinned down either. Schlick himself was critical of the manifesto of 1929 and gave a
brief vision statement of his own in “The Turning Point in Philosophy” (1930). A long-planned book by
Waismann of updates on Wittgenstein's thought, to which Schlick was extremely sympathetic, was never
completed as originally planned and only appeared posthumously (Waismann 1965; for earlier material
see Baker 2003). Comparison with rough transcripts of the Circle's discussions in the early 1930s (for
transcripts from between December 1930 and July 1931 see Stadler 1997 [2001, 241-299]) suggest that
Waismann's Wittgensteinian “Theses” (Waismann 1967 [1979, Appendix B]) come closest to an
elaboration of the orthodox Circle position at that time. Again, what needs to be stressed is that all of the
Circle's publications are to be understood as contributions to ongoing discussions among its members and
associates.
Despite the pluralism of the Vienna Circle's views, there did exist a minimal consensus which may be put
as follows. A theory of scientific knowledge was propagated which sought to renew empiricism by
freeing it from the impossible task of justifying the claims of the formal sciences. It will be noted that this
updating did not leave empiricism unchanged.
Following the logicism of Frege and Russell, the Circle considered logic and mathematics to be analytic
in nature. Extending Wittgenstein's insight about logical truths to mathematical ones as well, the Circle
considered both to be tautological. Like true statements of logic, mathematical statements did not express
factual truths: devoid of empirical content they only concerned ways of representing the world, spelling
out implication relations between statements. The knowledge claims of logic and mathematics gained
their justification on purely formal grounds, by proof of their derivability by stated rules from stated
axioms and premises. (Depending on the standing of these axioms and premises, justification was
conditional or unconditional.) Thus defanged of appeals to rational intuition, the contribution of pure
reason to human knowledge (in the form of logic and mathematics) was thought easily integrated into the
empiricist framework. (Carnap sought to accommodate Gödel's incompleteness results by separating
analyticity from effective provability and by postulating arithmetic to consist of an infinite series of ever
richer arithmetical languages; see the discussion and references in section 3.2 below.)
The synthetic statements of the empirical sciences meanwhile were held to be cognitively meaningful if
and only if they were empirically testable in some sense. They derived their justification as knowledge
claims from successful tests. Here the Circle appealed to a meaning criterion the correct formulation of
which was problematical and much debated (and will be discussed in greater detail in section 3.1 below).
Roughly, if synthetic statements failed testability in principle they were considered to be cognitively
meaningless and to give rise only to pseudo-problems. No third category of significance besides that of a
priori analytical and a posteriori synthetic statements was admitted: in particular, Kant's synthetic a
priori was banned as having been refuted by the progress of science itself. (The theory of relativity
showed what had been held to be an example of the synthetic a priori, namely Euclidean geometry, to be
false as the geometry of physical space). Thus the Circle rejected the knowledge claims of metaphysics as
being neither analytic and a priori nor empirical and synthetic. (On related but different grounds, they
also rejected the knowledge claims of normative ethics: whereas conditional norms could be grounded in
11
means-ends relations, unconditional norms remained unprovable in empirical terms and so depended
crucially on the disputed substantive a priori intuition.)
Given their empiricism, all of the members of the Vienna Circle also called into question the principled
separation of the natural and the human sciences. They were happy enough to admit to differences in their
object domains, but denied the categorical difference in both their overarching methodologies and
ultimate goals in inquiry, which the historicist tradition in the still only emerging social sciences and the
idealist tradition in philosophy insisted on. The Circle's own methodologically monist position was
sometimes represented under the heading of “unified science”. Precisely how such a unification of the
sciences was to be effected or understood remained a matter for further discussion (see section 3.3 below).
It is easy to see that, combined with the rejection of rational intuition, the Vienna Circle's exclusive
apportionment of reason into either formal a priori reasoning, issuing in analytic truths (or contradictions),
and substantive a posteriori reasoning, issuing in synthetic truths (or falsehoods), severely challenged the
traditional understanding of philosophy. All members of the Circle hailed the end of distinctive
philosophical system building. In line with the Tractatus claim that all philosophy is really a critique of
language, the Vienna Circle took the so-called linguistic turn, the turn to representation as the proper
subject matter of philosophy. Philosophy itself was denied a separate first-order domain of expertise and
declared a second-order inquiry. Whether the once queen of the sciences was thereby reduced to the mere
handmaiden of the latter was still left open. It remained a matter of disagreement whether philosophy was
also denied wholly autonomous sources of insight and what type of insight, if any, that would be. Just as
importantly, the tools of modern logic were employed also for metatheoretical construction, not just for
the reduction of empirical claims to their observational base. For the price of foundationalist certainty this
allowed for an enormous expansion of the domain of empirical discourse. Ultimately, it opened the space
for the still ongoing discussions of scientific realism and its alternatives (see section 3.4 below).
The Circle's leading protagonists differed in how they conceptualized this reflexive second-order inquiry
that the linguistic turn had brought on. Nevertheless, they all agreed broadly that the ways of representing
the world were largely determined by convention. A multitude of ideas hide behind this invocation of
conventionality. One particularly radical one is the denial of the apodicity of all apriority, the denial of the
claim that knowledge justified through reason alone represents truths that are unconditionally necessary.
Another one is the imputation of agency in the construction of the logico-linguistic frameworks that make
human cognition possible, the denial that conventionality could only mean acquiescence in tradition.
Whether such ideas were followed by individual members of the Circle, however, depended on their own
interests and influences. It is these often overlooked or misunderstood differences that hold the key to
understanding the interplay of occasionally incompatible positions that make up Vienna Circle
philosophy. (As can be seen from some of their internal disputes, moreover, these differences were also
not always obvious to the protagonists themselves.)
To see a striking example, consider their overarching conceptions of philosophy itself. Some protagonists
retained the idea that philosophy possessed a separate disciplinary identity from science and, like Schlick,
turned philosophy into a distinctive, albeit non-formal activity of meaning determination. Others, like
Carnap, agreed on the distinction between philosophy and science but turned philosophy into a purely
formal enterprise, the so-called logic of science. Still others went even further and, like Neurath under the
banner of “unified science”, also rejected philosophy as a separate discipline and apportioned what
remained of it after the rejection of metaphysics to science as its meta-theory. With Schlick, then,
philosophy became the activity of achieving a much clarified and deepened understanding of the
cognitive and linguistic practices actually already employed in science and everyday discourse. By
contrast, for Carnap, philosophy investigated, reconstructed and developed new logico-linguistic
frameworks and suggested possible formal conventions for science, while, for Neurath, philosophy was
replaced by an interdisciplinary meta-theory of science that encompassed formal as well as empirical
disciplines with a pragmatic orientation. Thus we find in competition different conceptions of postmetaphysical philosophy: the projects of experiential meaning determination, of formal rational
reconstruction and of naturalistic explications of leading theoretical and methodological notions. (For
roughly representative essay-length statements of their positions see Schlick 1930, Carnap 1932a and
Neurath 1932a.) In the more detailed discussions below these differences of overall approach will figure
repeatedly.
12
Criticisms of the basic positions adopted in the Vienna Circle are legion, though it may be questioned
whether most of them took account of the sophisticated variations on offer. (Sometimes the Circle's own
writings are disregarded altogether and “logical positivism” is discussed only via the proxy of Ayer's
popular exposition; see, e.g., Soames 2003.) But some Neo-Kantians like Ernst Cassirer may claim that
they too accepted developments like the merely relative a priori and an appropriate conception of the
historical development of science. Likewise, Wittgensteinians may claim that Wittgenstein's own
opposition to metaphysics only concerned false attempts to render it intelligible: his merely ineffable but
uneliminated metaphysics concerned precisely what for him were essentials of ways of representing the
world. The commonest criticisms, however, concerned not the uniqueness of the Vienna Circle's insights,
or their faithfulness to their supposed sources, but whether they were insights at all. Prominent objects of
this type of criticism include the verificationist theory of meaning and its claimed anti-metaphysical and
non-cognitivist consequences as well as its own status of meaningfulness; the reductionism in
phenomenalist or physicalist guises that appeared to attend the Circle's attempted operationalisation of the
logical atomism of Russell and Wittgenstein; and the Circle's alleged scientism in general and their
formalist and a-historical conception of scientific cognition in particular. These criticisms are discussed in
some detail below in order to assess why which of the associated doctrines remain of what importance.
As noted, the Vienna Circle did not last long: its philosophical revolution came at a cost. Yet what was so
socially, indeed politically, explosive about what appears on first sight to be a particularly arid, if not
astringent, doctrine of specialist scientific knowledge? To a large part, precisely what made it so
controversial philosophically: its claim to refute opponents not by proving their statements to be false but
by showing them to be (cognitively) meaningless. Whatever the niceties of their philosophical argument
here, the socio-political impact of the Vienna Circle's philosophies of science was obvious and profound.
All of them opposed the increasing groundswell of radically mistaken, indeed irrational, ways of thinking
about thought and its place in the world. In their time and place, the mere demand that public discourse be
perspicuous, in particular, that reasoning be valid and premises true—a demand implicit in their general
ideal of reason—placed them in the middle of crucial socio-political struggles. Some members and
sympathisers also actively opposed the then increasingly popular völkisch supra-individual holism in
social science as a dangerous intellectual aberration. Not only did such ideas support racism and fascism
in politics, but they themselves were supported only by radically mistaken arguments concerning the
nature and explanation of organic and unorganic matter. One thing, then, that made all of the Vienna
Circle philosophies politically relevant was the contingent fact that in its day much political discourse
exhibited striking epistemic deficits. That some of the members of the Circle went, without logical
blunders, still further by arguing that socio-political considerations can play a legitimate role in some
instances of theory choice due to underdetermination is yet another matter. Here this particular issue, as
well as the general topic of the Circle's embedding in modernism and the discourse of modernity, will not
be pursued further. (See Putnam 1981b for a reductionist, Galison 1990 for a foundationalist, Uebel 1996
for a constructivist reading of their modernism.)
Given only the outlines of Vienna Circle philosophy, its controversial character is evident. The boldness
of its claims made it attractive but that boldness also seemed to be its undoing. Turning to the questions of
how far and, if at all, which forms of Vienna Circle philosophy stand up to some common criticisms, both
the synchronic variations and the diachronic trajectories of its variants must be taken into account. This
will be attempted in the sections below.
Before expectations are raised too high, however, it must also remembered that in this article only the
views of members of the Vienna Circle can be discussed, even though the problematic issues were
pervasive in logical empiricism generally. What will be noted, however, is that Vienna Circle philosophy
was by no means identical with the post-World War II logical empiricism that has come to be known as
the “received view” of scientific theories, even though it would be hard to imagine the latter without the
former.
To deepen the somewhat cursory overview of Vienna Circle philosophy given above, we now turn to the
discussion of the following issues: first, the viability of the conceptions of empirical significance
employed by Vienna Circle in its classical period; second, its uses of the analytic-synthetic distinction;
third, its supposedly reductionist designs and foundationalist ambitions for philosophy; fourth, its stances
in the debate about realism or anti-realism with regard to the theoretical terms in science; fifth, Carnap's
later ideas in response to some of the problems encountered; sixth, the issue of the status of the meaning
criterion itself and of the point of their critique of metaphysics; seventh, the Vienna Circle's attitude
towards history and of their own place in the history of philosophy.
13
These topics have been chosen for the light their investigation throws on the Circle's own agendas and the
reception of its doctrines amongst philosophers at large, as well as for the relative ease with which their
discussion allows its development and legacy to be charted. There can be little doubt about the enormous
impact that the members of the Vienna Circle had on the development of twentieth-century philosophy.
What is less clear is whether any of its distinctive doctrines are left standing once the dust of their
discussion has settled or whether those of its teachings that were deemed defensible merged seamlessly
into the broad church that analytic philosophy has become (and, if so, what those surviving doctrines and
teachings may be).
It must be noted, then, that the topics chosen for this article do not exhaust the issues concerning which
the members of the Vienna Circle made significant contributions (which continue to stimulate work in the
history of philosophy of science). Important topics like that of the theory and practice of unified science,
of the nature of the empirical basis of science and of the general structure of the theories of individual
sciences can only be touched upon selectively. Likewise, while the general topic of ethical noncognitivism receives two passing mentions, the Circle's varied approaches to value theory cannot be
discussed here (see Rutte 1986). Other matters, like the contributions made by Vienna Circle members to
the development of probability theory and inductive logic, the philosophy of logic and mathematics (apart
from the guiding ideas of Carnap) and to the philosophy of individual empirical sciences (physics,
biology, psychology, social science), cannot be discussed at all (see Creath and Friedman forthcoming
and Richardson and Uebel forthcoming for relevant essays).
Not surprisingly, it was the Circle's rejection of metaphysics by means of their seemingly devastating
criterion of cognitive significance that attracted immediate opposition. (That they did not deny all
meaning to statements thus ruled out of court was freely admitted from early on, but this “expressive”
surplus was considered secondary to so-called “cognitive” meaning and discountable in science (see
Carnap 1928b, 1932a).) Notwithstanding the metaphysicans' thunder, however, the most telling criticisms
of the criterion came from within the Circle or broadly sympathetic philosophers. When it was protested
that failure to meet an empiricist criterion of significance did not make philosophical statements
meaningless, members of the Circle simply asked for an account of what this non-empirical and
presumably non-emotive meaning consisted in and typically received no convincing answer. The
weakness of their position was rather that their own criterion of empirical significance resisted an
acceptable formal characterization.
To start with, it must be noted that long before the verification principle proper entered Circle's discourse
around 1930, the thought expressed by Mach's dictum that “where neither confirmation nor refutation is
possible, science is not concerned” (1883 [1960, 587]) was accepted as a basic precept of critical
reflection about science. Responsiveness to evidence for and against a claim was the hallmark of
scientific discourse. (Particularly the group Frank-Hahn-Neurath, who formed part of pre-World War I
discussion group (Frank 1941, 1949a) sometimes called the “First Vienna Circle” (Haller 1985, Uebel
2003), can be presumed to be familiar with Mach's criterion.) Beyond this, still in the 1920s, Schlick
(1926) convicted metaphysics for falsely trying to express as logically structured cognition what is but the
inexpressible qualitative content of experience. Already then, however, Carnap (1928b, §7) edged
towards a formal criterion by requiring empirically significant statements to be such that experiential
support for them or for their negation is at least conceivable. Meaningfulness meant the possession of
“factual content” which could not, on pain of rendering scientific hypotheses meaningless, be reduced to
actual testability. Instead, the empirical significance of a statement had to be conceived of as possession
of the potential to receive direct or indirect experiential support (via deductive or inductive reasoning).
In 1930, considerations of this sort appeared to receive a considerable boost due to Waisman's reports of
Wittgenstein's pronouncement that the meaning of a proposition is its method of verification.
(Wittgenstein discussed the thesis “The meaning of its sentence is its verification” in conversations with
Schlick and Waismann on 22 December 1929 and 2 January 1930 (see Waismann 1967 [1979]). The
thesis was elaborated in Waismann's “Theses” dated to “around 1930” which were presented as
Wittgenstein's considered views.) While Wittgenstein may have thought of this statement more as a
constitutive principle of meaning, in the Circle it was put to work primarily as a demarcation criterion
against metaphysics, albeit typically based on an underlying theory of meaning. Note that even though
this early Wittgensteinian version of the meaning criterion required conclusive verifiability (which
Carnap's of 1928 did not), it also allowed for verifiability in principle only (and did not demand actual
verifiability). Like Carnap's notion of experiential support, this criterion worked with the mere
conceivability of verifiability. (The demand for conclusive verifiability was discussed in the meetings
14
with Wittgenstein.) Around 1931, however, it had become clear to some that this would not do. What
Carnap later called the “liberalization of empiricism” was underway and different camps became
discernible within the Circle. It was over this issue that the so-called “left wing” with Carnap, Hahn,
Frank and Neurath first distinguished itself from the “more conservative wing” around Schlick. (See
Carnap 1936-37, 422 and 1963a, §9. Carnap 1936-37, 37n dated the opposition to strict verificationism to
“about 1931”.)
In the first place, this liberalization meant the accomodation of universally quantified statements and the
return, as it were, to salient aspects of Carnap's 1928 conception. Everybody had noted that the
Wittgensteinian verificationist criterion rendered universally quantified statements meaningless. Schlick
(1931) thus followed Wittgenstein's own suggestion to treat them instead as representing rules for the
formation of verifiable singular statements. (His abandonment of conclusive verifiability is indicated only
in Schlick 1936a.) By contrast, Hahn (1933, drawn from lectures in 1932) pointed out that hypotheses
should be counted as properly meaningful as well and that the criterion be weakened to allow for less than
conclusive verifiability. But other elements played into this liberalization as well. A second element that
began to do so soon was the recognition of the problem of the irreducibility of disposition terms to
observation terms (more on this presently). A third element was that disagreement arose as to whether the
in-principle verifiability or support turned on what was merely logically possible or on what was
nomologically possible, as a matter of physical law etc. A fourth element, finally, was that differences
emerged as to whether the criterion of significance was to apply to all languages or whether it was to
apply primarily to constructed, formal languages. Schlick retained the focus on logical possibility and
natural languages throughout, but Carnap had firmly settled his focus on nomological possibility and
constructed languages by the mid-thirties. Concerned with natural language, Schlick (1932, 1936a)
deemed all statements meaningful for which it was logically possible to conceive of a procedure of
verification; concerned with constructed languages only, Carnap (1936-37) deemed meaningful only
statements for whom it was nomologically possible to conceive of a procedure of confirmation of
disconfirmation.
Many of these issues were openly discussed at the Paris congress in 1935. Already in 1932 Carnap had
sought to sharpen his previous criterion by stipulating that those statements were meaningful that were
syntactically well-formed and whose non-logical terms were reducible to terms occurring in the basic
observational evidence statements of science. While Carnap's focus on the reduction of descriptive terms
allows for the conclusive verification of some statements, it must be noted that his criterion also allowed
universally quantified statements to be meaningful, provided they were syntactically and terminologically
correct (1932a, §2). It was not until one of his Paris addresses, however, that Carnap officially declared
the meaning criterion to be mere confirmability. Carnap's new criterion required neither verification nor
falsification but only partial testability so as now to include not only universal statements but also the
disposition statements of science (see Carnap 1936-37; the English translation of the original Paris
address (1936 [1949]) combines it with extraneous material). These disposition terms were thought to be
linked to observation statements by a variety of reduction postulates and possibly even long reduction
chains, all of which provided non-eliminative partial definitions (despite their name they provided no
eliminative reductions). Though plausible initially, the device of introducing non-observational terms in
this way gave rise to a number of difficulties which impugned the supposedly clear distinctions between
logical and empirical matters and analytic and synthetic statements (Hempel 1951). Independently,
Carnap himself (1939) soon gave up the hope that all theoretical terms of science could be related to an
observational base by such reduction chains. This admission raised a serious problem for the formulation
of a meaning criterion: how was one to rule out unwanted metaphysical claims while admitting as
significant highly abstract scientific claims?
Consider that Carnap admitted as legitimate theoretical terms that may be merely implicitly defined in
calculi that are themselves only partially interpreted by correspondence rules between some select
calculus terms and expressions belonging to an observational language (via non-eliminative reductions).
The problem was that mere confirmability was simply too weak a meaning criterion to rule out some
putative metaphysical claims. Moreover, this problem arose for both the statement-based approach to the
criterion (taken by Carnap in 1928, by Wittgenstein in 1929/30, and by Ayer both in the first (1936) and
the second editions (1946) of Language Truth and Logic) and for the term-based approach (taken by
Carnap since 1932). For the former approach, the problem was that the empirical legitimacy of statements
obtained via indirect testing also transfered to any expressions that could be truth-functionally conjoined
to them (for instance, by the rule of ‘or’-introduction). Statements thus became empirically significant,
however vacuous they had been on their own. For the term-based approach, the problem was that, given
15
the non-eliminability of dispositional and theoretical terms, empirical significance was no longer
ascribable to individual expressions in isolation but became a holistic affair, with little guarantee in turn
for the empiricist legitimacy of all the terms now involved.
For most critics (even within the ranks of logical empiricism), the problem of ruling out metaphysical
statements while retaining the terms of high theory remained unsolved. By 1950, in response to the
troubles of Ayer's two attempts to account for the indirect testing of theoretical statements via their
consequences, Hempel conceded that it was “useless to continue to search for an adequate criterion of
testability in terms of deductive relationships to observation sentences” (1950 [1959, 116]). The following
year, Hempel also abandoned the idea of using, as a criterion of empirical significance, Carnap's method
of translatability into an antecedently determined empirical language consisting only of observational
non-logical vocabulary. Precisely because it was suitably liberalized to allow abstract scientific theories
with merely partial interpretations, its anti-metaphysical edge was blunted: it allowed for combination
with “some set of metaphysical propositions, even if the latter have no empirical interpretation at all”
(1951, 70). Hempel drew the holistic conclusion that the units of empirical significance were entire
theories and that the measure of empirical significance itself was multi-criterial and, moreover, allowed
for degrees of significance. To many, this amounted to the demise of the Circle's anti-metaphysical
campaign. By contrast, Feigl's reaction (1956) was to reduce the ambition of the criterion of significance
to the mere provision of necessary conditions.
Some further work was undertaken on rescuing and, again, debunking a version of the statement-based
criterion, but not by (former) members of the Vienna Circle. However, in response to the problem of how
to formulate a meaning criterion that suitably distinguished between empirically significant and
insignificant non-observational terms, Carnap proposed a new solution in 1956 and another one in 1966.
We will return to discuss these separately (see section 3.5 below); for now we need only note that these
proposals were highly technical and applied only to axiomatized theories in formal languages. They too,
however, found not much favor amongst philosophers. Yet whatever the problems that may or may not
beset them, it would seem that far more general philosophical considerations contributed to the
disappearance of the problem of meaning criterion from most philosophical discussions since the early
1960s (other than as an example of mistaken positivism). These include the increasing opposition to the
distinctions between analytic and synthetic statements and observational and theoretical terms as well as a
general sense of dissatisfaction with Carnap's approach to philosophy which began to seem both too
formalist in execution and too deflationary in ambition. The entire philosophical program of which the
search for a precise criterion of empirical significance was a part had begun to fall out of favor (and with
it technical discussions about the criterion's latest version).
The widely perceived collapse of the classical Viennese project to find in an empiricist meaning criterion
a demarcation criterion against metaphysics—we reserve judgement about Carnap's last two proposals
here—can be interpreted in a variety of ways. It strongly suggests that cognitive significance cannot be
reduced to what is directly observable, whether that be interpreted in phenomenalist or intersubjective,
physicalist terms. In that important but somewhat subsidiary sense, the collapse spelt the failure of many
of the reductivist projects typically ascribed to Viennese neopositivism (but see section 3.3 below).
Beyond that, what actually had failed was the attempt to characterize for natural languages the class of
cognitively significant propositions by recursive definitions in purely logical terms, either by relations of
deducibility or translatability. What failed, in other words, was the attempt to apply a general conception
of philosophical analysis as purely formal, pursued also in other areas, to the problem of characterizing
meaningfulness.
This general conception can be considered formalist in several senses. It was formalist, first, in
demanding the analysis of the meaning of concepts and propositions in terms of logically necessary and
sufficient conditions: it was precise and brooked no exceptions. And it was formalist, second, in
demanding that such analyses be given solely in terms of the logical relations of these concepts and
propositions to other concepts and propositions: it used the tools of formal logic. There is also a third
sense that is, however, applicable predominantly to the philosophical project in Carnap's hands, in that it
was formalist since it concentrated on the analysis of contested concepts via their explication in formal
languages. (Discussion of its viability must be deferred until sections 3.5 and 3.6 below, since here we are
concerned with the formalist project as applied to concepts in natural language.) The question arises
whether all Vienna Circle philosophers concerned with empirical significance in natural language were
equally affected, for the collapse of the formalist project may leave as yet untouched other ways of
sustaining the objection that metaphysics is, in some relevant sense, cognitively insignificant. (Such
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philosophers in turn would have to answer the charge, of course, that only the formalist project of
showing metaphysics strictly meaningless rendered the Viennese anti-metaphysics distinctive.)
Even though the formalist project became identified with mainstream logical empiricism generally
(consider its prominence in confirmation theory and in the theory of explanation), it was not universally
subscribed to in the Vienna Circle itself. In different ways, neither Schlick nor Neurath or Frank adhered
to it. As noted in the overview above, Schlick's attempts to exhibit natural language meaning abjured
efforts to characterize it in explicitly formal terms, even though he accepted the demand for necessary and
sufficient conditions of significance. In the end, moreover, Schlick turned away from his colleagues'
search for a criterion of empirical significance. In allowing talk of life after death as meaningful (1936a),
for the very reason that what speaks against it is only the empirical impossibility of verifying such talk,
Schlick's final criterion clearly left empiricist strictures behind.
By contrast, Neurath and Frank kept their focus on empirical significance. While they did not discuss
these matters explicitly, their writings give the impression that Neurath and Frank chose to adopt (if not
retain) a contextual, exemplar-based approach to characterizing the criterion of meaninglessness and so
decided to forego the enumeration of necessary and sufficient conditions. Mach's precept cited earlier is
an example of such a pragmatic approach, as is, it should be noted, Peirce's criterion of significance,
endorsed by Quine (1969), as making no discernible difference whether its propositions are likely to be
true or false. Mach's pragmatic approach had been championed already before verificationism proper by
Neurath, Frank and Hahn who became, like Carnap, early opponents of conclusive verifiability. (Indeed,
it is doubtful whether Neurath's radical fallibilism, most clearly expressed already in 1913, ever wavered.)
Its renewal found clear expression in Neurath's adoption (1935a, 1938) of K. Reach's formulation of
metaphysical statements as “isolated” ones, as statements that do not derive from and hold no
consequences for those statements that we do accept on the basis of empirical evidence or for logical
reasons. (Hempel's dismissal, in 1951, of this pragmatic indicator presupposes the desiderata of the
formalist project.) It is worth investigating whether—if the critique of the alleged reductionist ambitions
of their philosophy could also be deflected—the impetus of the anti-verificationist critique could be
absorbed by those with a pragmatic approach to the demarcation against metaphysics. Much as with
Quine's Peirce, such a criterion rules out as without interest for epistemic activity all concepts and
propositions whose truth or falsity make no appreciable difference to the sets of concepts and propositions
we do accept already. As noted, however, in merging with the broader stream of pragmatism, the most
prominent and distinctive trait of Vienna Circle anti-metaphysics would thus be given up.
An entirely different moral was drawn by Reichenbach (1938) and thinkers indebted to his probabilistic
conception of meaning and his probabilistic version of verificationism, which escaped the criticisms
surveyed above by vagaries of its own. Such theorists perceive the failure of the formalist model to
accommodate the empirical significance of theoretical terms to stem from its so-called deductive
chauvinism. In place of the exclusive reliance on the hypothetical-deductive method these theorists
employ non-demonstrative analogical and causal inductive reasoning to ground theoretical statements
empirically. Like Salmon, these theorists adopt a form of “non-linguistic empiricism” which they sharply
differentiate from the empiricism of the Vienna Circle (Salmon 1985, 2003 and Parrini 1998).
Now against both the pragmatic and the post-linguistic responses to the perceived failure of the attempt to
provide a precise formal criterion of significance serious worries can be raised. Thus it must be asked
whether without a precise way of determining when a statement ‘makes an appreciable difference’,
criticism of metaphysics based on such a criterion may be not be considered as a biased dismissal rather
than a demonstration of fact and so fall short of what is needed. Likewise in the case of the antideductivist response, it must be noted that a criterion based on analogical reasoning will only be as
effective as the strength of the analogy which can always be criticized as inapt (and similarly for appeals
to causal reasoning). The very point of exact philosophy in a scientific spirit—for many the very point of
Vienna Circle philosophy itself—seems threatened by such maneuvres. Acquiescence in the perceived
failure of the proposed criteria of significance thus comes with a price: if not that of abandoning Vienna
Circle philosophy altogether, then that of having to formulate an alternative to Carnap's version of it.
(Recent reconstructive work on Neurath and Frank may be understood in this light.)
A still different response—but one emblematic for the philosophical public at large—is that of another of
Reichenbach's former students, Putnam, who has come to reject the anti-metaphysical project that
powered verificationism in its entirety. Repeatedly in his later years, Putnam has called for a refashioning
17
of analytic philosophy as such, providing, as it were, a philosophically conservative counterweight to
Rorty's turn to postmodernism. Putnam's reasons (the alleged self-refutation of the meaning criterion) are
still different from those surveyed above and will be discussed when we return to reconsider the very
point of the Circle's campaign against metaphysics (see section 3.6 below).
Whether the criterialist agenda was pursued in a formalist or pragmatic vein, however, all members
shared the belief that meaningful statements divided exclusively into analytic and synthetic statements
which, when asserted, were strictly matched with a priori and a posteriori reasoning for their support.
The Vienna Circle wielded this pairing of epistemic and semantic notions as a weapon not only against
the substantive a priori of the Schoolmen but also against Kant's synthetic a priori.
It is well known that one component of the Vienna Circle's arsenal, the analytic/synthetic distinction,
came under sharp criticism from Quine in his “Two Dogmas of Empiricism” (1951a), less so that the
criticism can only be sustained by relying on objections of a type first published by Tarski. The argument
is more complex, but here is a very rough sketch. So as to discard the analytic/synthetic distinction as an
unwarranted dogma, Quine in “Two Dogmas” argued for the in-principle revisability of all knowledge
claims and criticised the impossibility of defining analyticity in a non-circular fashion. The first argument
tells against the apodictic a priori of old, but, as we shall see, it is unclear whether it tells against at least
some of the notions of the a priori held in the Vienna Circle. The second argument presupposes a
commitment to extensionalism that likewise can be argued not to have been shared by all in the Circle. By
contrast, Tarski had merely observed that, at a still more fundamental level, he knew of no basis for a
sharp distinction between logical and non-logical terms. (For relevant primary source materials see also
Quine 1935, 1951b, 1963, Carnap 1950, 1955, 1963b, their correspondence and related previously
unpublished lectures and writings in Creath 1990, the memoir Quine 1992, and Tarski 1936 and Mancosu
2005.)
The central role on the Vienna Circle's side in this discussion falls to Carnap and the reorientation of
philosophy he sought to effect in Logical Syntax. His notion of the merely relative and therefore nonapodictic a priori deeply conditioned his notion of analyticity—comprising both logical and mathematical
truths—and allowed him to sidestep Quine's fallibilist argument in a most instructive fashion. But let's
first consider Schlick as a contrast class. Schlick (1934) appeared to show little awareness of the
language-relativity of the analytic/synthetic distinction and spoke of analytic truths as conceptual
necessities that can be conclusively surveyed. This would suggest that Schlick rejected Kant's apodictic
synthetic a priori but not the apodicity of analytic statements. Clearly, if that were so, Quine's argument
from universal fallibilism would find a target here. Matters are not quite so clear-cut, however. Schlick
had long accepted the doctrine of semantic conventionalism that the same facts could be captured by
different conceptual systems (1915): his analytic truths were also framework-relative and necessary only
in the very frameworks they themselves helped to constitute. Yet what Schlick did not countenance were
incommensurable conceptual frameworks: for him facts and conventions were always sharply separable
(1936b). As a result, Schlick did not accept the possibility that after the adoption of a new framework the
analytic truths of the old one may be no longer assertable. Therein lay the weakness Quine's argument
could exploit: analytic truths remained unrevisable in a strong sense.
Now Carnap, under the banner of the principle of logical tolerance (1934/37, §17), abandoned the idea of
the one universal logic which had informed Frege, Russell and Wittgenstein before him. Instead, he
recognized a plurality of logics and languages whose consistency was an objective matter even though
axioms and logical rules were fixed entirely by convention. Already due to this the framework-relativity
of analytic statements went deeper for Carnap than it did for Schlick. But Carnap also accepted the
possibility of incommensurability between seemingly similar descriptive terms and between entire
conceptual systems (1936). Accepting the analytic truths of the framework of our best physical theory
may thus be incompatible with accepting those of an earlier one, even if the same logic is employed in
both. Carnapian analyticities do not therefore express propositions that we hold to be true unconditionally,
nor true merely relative to their own framework. They are unrevisable only in a weak sense, in that their
proper framework itself may become inapplicable and so get discarded. Quine's claim of universal
revisability (which itself needs some modification; see Putnam 1978) thus misses its mark against them.
Quine, of course, rejected Carnap's intensionalist accommodation of radical fallibilism.
Concerning the criticism of the circular nature of the definition of analyticity, Carnap responded that it
pertained primarily to the idea of analyticity in natural language whereas he was interested in
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“explications” as provided by the logic of science (or better, a logic of science, since there existed no
unique logic of science for Carnap). Explications are reconstructions in a formal language of selected
aspects of complex terms that should not be expected to model the original in all respects (1950b, Ch.1).
Moreover, Carnap held that explication of the notion of analyticity in formal languages yielded the kind
of precision that rendered the complaint of circularity irrelevant: vague intuitions of meaning were no
longer relied upon. Those propositions of a given language were analytic that followed from its axioms
and, once the syntactic limitations of the Logical Syntax period had been left behind, from its definitions
and meaning postulates, by application of its rules: no ambiguity obtained.
So it may appear that the notion of analyticity is easily delimitable in Carnap's explicational approach:
analytic propositions would be those that constitute a logico-linguistic framework. But complications
arose from the fact that, on Carnap's understanding, not all propositions defining a logico-linguistic
framework need be analytic ones (1934/37, §51). It was possible for a framework to consist not only of Lrules, whose entirety determines the notion of logical consequence, but also of P-rules, which represent
presumed physical laws. So let analytic propositions be those framework propositions whose negations
are self-contradictory. Here a problem arose once the syntactic constraints were dropped by Carnap after
Logical Syntax so as to allow semantic reasoning and the introduction of so-called meaning postulates:
now the class of analytic propositions was widened to include not only logical and mathematical truths
but also those obtained by substitution of semantically equivalent expressions. How was one now to
explicate the idea that there can be non-analytic framework propositions (whose negations are not selfcontradictory)? For opponents like Quine, responding that the negations of non-analytic framework
propositions do not contradict meaning postulates, was merely to dress up a presupposed notion of
meaning in pseudo-formal garb: while it provided what looked like formal criteria, Carnap's method did
not leave the circle of intensional notions behind and so seemed to beg the question. Meaning postulates,
after all, could only be identified by appearing on a list headed “meaning postulates”.
Here one must note that in Logical Syntax, Carnap also modified the thesis of extensionality he had
previously defended alongside Russell and Wittgenstein: now it merely claimed the possibility of purely
extensional langages and no longer demanded that intensional languages be reduced to them (ibid., §67).
Of course, the mere claim that the language of science can be extensional still proves troublesome enough,
given that in such a language a distinction between laws and accidentally true universal propositions
cannot be drawn (the notion of a counterfactual conditional, needed to distinguish the former, is an
intensional one). Even so, this opening of Carnap's towards intensionalism already at the height of his
syntacticism seems enough to thwart Quine's second complaint in “Two Dogmas”—to say nothing of his
explicit intensionalism in Meaning and Necessity (1947). Quite obviously, Carnap did not share Quine's
extensionalist agenda, so the need to break out of the circle of intensional notions once these were clearly
defined in his formal languages did not apply. That their's were in fact different empiricist research
programmes was insufficiently stressed, it would appear, by Quine and Quinean critics of Carnap (Stein
1992; cf. Ricketts 1982, 2003, Creath 1991, 2004, Richardson 1997).
To sustain his critique, Quine had to revive his and Tarski's early doubts about Carnap's methodological
apparatus and dig even deeper. (Tarski also shared Quine's misgivings about analyticity when they
discussed these issues with Carnap at Harvard; see Carnap 1942, Preface.) Their scepticism found its
target in Carnap's ingenious measures in Logical Syntax taken to preserve the thesis that mathematics is
analytic from the ravages of Gödel's incompleteness theorems. Gödel proved that every formal system
strong enough to represent number theory contains a formula that is true but neither itself or its negation
is provable in that system; such formulae—known since as Gödel sentences—are provable in a still
stronger system which, however, also contains a formula of its own that is true but not provable in it (and
neither is its negation). Commonly, Gödel's proof is taken to have undermined the thesis of the analyticity
of arithmetic. (For discussions of this challenge to Carnap's logical syntax project, see Friedman 1988,
1999a, Goldfarb and Ricketts 1992, Richardson 1994, Awodey and Carus 2004.) Carnap responded by
stating that arithmetic demands an infinite sequence of ever richer languages and by declaring analytic
statements to be provable by non-finite reasoning (1934/37, §60a-d). This looked like fitting the bill on
purely technical grounds, but it is questionable whether such reasoning may still count as syntactic.
Nowadays, it is computational effectiveness that is taken to distinguish purely formal from non-formal,
material reasoning. (Carnap's move highlights the tension within Logical Syntax between formal and
crypto-semantic reasoning. It thus points ahead to his acceptance of semantics in 1935—only one year
after the publication of Logical Syntax and contrary to his opposition against it expressed in that book—
that the rigid syntacticism officially advertised there was at the same time undermined as its failings were
being compensated (illegitimately so by official standards), e.g., by considering translatability a syntactic
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notion. For a discussion of Carnap's move, see Coffa 1978, Ricketts 1996, Goldfarb 1997, Creath 1996,
1999.) Still, accepting analyticity as a semantic notion is itself unproblematic (and Carnap was aware that
his reconstruction of arithmetic was not standard logicism).
Now Tarski (1936) granted the language-relativity of the reconstructed (narrow) notion of analyticity in
Logical Syntax. He also did not object that Carnap's procedure of circumventing the problem which the
Gödel sentences presented to the thesis of the analyticity of arithmetic was illegitimate. Tarski rather
questioned whether there were “objective reasons” for the sharp distinction between logical and nonlogical terms. In doing so he pointed out that Carnap's way of treating analyticity reflected a certain
flexibility in the distinction between the logical and the empirical: that distinction itself was not a hard
and fast one. Since noting that the distinction between logical and non-logical was not a sharp one and
arguing that no principled distinction could be upheld between them are two quite different reactions,
however, Tarski's point on its own does not fully support the Quinean critique. Quine's conclusion (1940,
§60) that the notion of logical truth itself is “informal” rather turns on his outright rejection of Carnap's
accommodation to Gödel's result of the thesis that arithmetic is analytic. It would seem to be this point
that ultimately motivated Quine to develop his naturalistic alternative to Carnap's conception of
philosophy.
Different strands of Quine's criticism of the analytic/synthetic distinction must thus be sharply
distinguished. While Quine's criticisms in “Two Dogmas” on their own clearly did not undermine all
forms of the distinction that were defended in the Vienna Circle—Carnap's reconstructions of the notion
of analyticity did not express unconditionally necessary and unrevisable propositions—they do gain in
plausibility even against Carnap's once it is recognized that the deepest ground of contestation lies
elsewhere: not in the notion of analyticity widely understood but in that of logical truth narrowly
understood. Read in this way, Quine can be seen to argue that the notion of L-consequence as explication
of analytic truth—as opposed to P-consequence as non-analytic, mere framework entailments—traded not
only on the idea of non-finitary notions of proof but also on a distinction of logical from descriptive
expressions that itself only proceded on the basis of a finite enumeration of the former (compare Carnap
1934/37, §§51-52). What Quine criticized was precisely the fact that Carnap could ground the distinction
between analytical statements (L-rules) and bare framework propositions (P-rules) no deeper than by the
bare enumeration of certain constituents of the framework itself: was the distinction therefore not quite
arbitrary? (That later on Carnap adopted a wider notion of analyticity than L-truth, namely, as truths
derivable from the L-truths and meaning postulates for the terms of the language, provided Quine with the
opening for his complaint about the circularity in defining intensional concepts, but that was but an
expansion of already contested territory. In fact, even the complications of the Logical Syntax conception
of logico-linguistic frameworks can be entirely neglected here: even if no P-rules are recognized, the
notion of L-consequence still depended on how the class of logical terms was delimited, namely, by
enumerations, and that was what was under fire all along.)
Quine's direct arguments against the distinction between logical and empirical truth (1963) have been
found to beg the question against Carnap and his way of conceiving of philosophy (Creath 2003). This
way of responding to Quine's objection requires us to specify still more precisely what Carnap thought he
was doing when he employed the distinction between analytic and synthetic propositions. To repeat,
rational reconstructions or explications did not seek to model natural language concepts in their tensionfilled vividness, but to make proposals for future use and to extract and systematize certain aspects for
constructive purposes. Late in his career Carnap clarified (1963b, §32) that he regarded the distinction
between analytic and synthetic statements—just like the distinction between descriptive or factual and
prescriptive or evaluative statements (similar considerations thus also apply to his version of ethical noncognitivism!)—not as descriptive of natural language practices, but as a constructive tool for logicolinguistic analysis and theory construction. (Even so, in (1955) he gave broadly behavioural criteria for
when any meaning proposals could be deemed accepted in linguistic practice.) It is difficult to overstress
the significance of this stance of Carnap's for the evaluation of his version of the philosophical project of
the Vienna Circle. Carnap's understanding of philosophy has been aptly described as the “science of
possibilities” (Mormann 2000).
We already saw that in Carnap's hands the analytic/synthetic distinction was no longer the traditional one
that, presupposing one underlying universal logic, strictly sorted (unqualifiedly) necessary statements
from contingent ones. But now it becomes clear that more still was at issue than the relativization of the
distinction to different logico-linguistic frameworks. As Carnap understood the analytic/synthetic
distinction, it was a distinction drawn by a logician to enable greater theoretical systematicity in the
20
reconstructive understanding of a given symbol system. That fully determinative objective criteria of
what to regard as a logical and what as a non-logical term cannot be assumed to be pre-given does not
then in and of itself invalidate the use of that distinction by Carnap. On the contrary, it has been
convincingly argued that Carnap himself did not hold to a notion of what is a factual and a formal
expression or statement that was independent of the specification of the language in question (Ricketts
1994). The ungroundedness of his basic semantic categories, all this suggests instead, was a fact that his
own theories fully recognized and consciously exploited. (Somewhat analogously, that we cannot define
science independently of the practice of scientists of “our culture” was admitted by Neurath 1932a,
Carnap 1932d and Hempel 1935, much to exasperation of Zilsel 1932 and Schlick 1935a.)
It remained open for Carnap then to declare his notion of analyticity to be only operationally defined for
constructed languages and to let that notion be judged entirely in terms of its utility for meta-theoretical
reflection. Just on that account, however, a last hurdle remains: finding a suitable criterion of significance
for theoretical terms that allows the distinction between analytic and synthetic statements to be drawn in
the non-observational, theoretical languages of science. (This was a problem ever since the noneliminative reducibility of disposition terms had been accepted and one that still held for Carnap's 1956
criterion; see section 3.5 below). Only if that can be done, we must therefore add, can Carnap claim his
formalist explicationist project to emerge entirely unscathed from the criticisms of both Tarski and Quine.
None of this is to deny, of course, that one can find understandings of the term “analytic” by members of
the Vienna Circle (like Schlick) that do fall victim to the criticisms of Quine more easily. Nor should one
discount the fact that Carnap's logic of science emerges as wilfully ill-equipped to deal with the problems
that exercise the traditional metaphysics or epistemology that deal in analyticities. (Of course, unlike his
detractors, Carnap considered this to be a merit of his approach.) Lastly, it must be noted that Carnap's
intensionalist logic of science holds out the promise of practical utility only for the price of a pragmatic
story that remains to be told. Of what nature are the practical considerations and decisions that, as Carnap
so freely conceded (1950a), are called for when choosing logico-linguistic frameworks? (Such
conventional choices do not respond to truth or falsity, but instead to whatever is taken to measure
convenience.) That Carnap rightly may have considered such pragmatic questions beyond his own
specific brief as a logician of science does not obviate the need for an answer to the question itself. On
this point, perhaps, more collaboration with Neurath and Frank, who were sympathetic to Carnap's
explication of analyticity but did not recur to it much in their own, more practice-oriented investigations,
would have been helpful.
As it happens, anti-verificationism has two aspects: opposition to meaning reductionism and opposition to
the formalist project. Turning to the former, we must distinguish two forms of reductionism,
phenomenalist and physicalist reductionism. Phenomenalism holds statements to be cognitively
significant if they can be reduced to statements about about one's experience, be it outer (senses) or inner
(introspection). Physicalism holds statements to be cognitively significant if they can be reduced or
evidentially related to statements about physical states of affairs. Here it must be noted that the Vienna
Circle is typically remembered in terms of the apparently phenomenalist ambitions of Carnap's Aufbau of
1928, but that already by the early 1930s some form of physicalism was favoured by some leading
members including Carnap (1932b) and that already in the Aufbau the possibility of a different basis than
the phenomenal one had been indicated. Thus one also must consider just how reductivist in intent this
physicalism was meant to be.
Considerations can begin with an early critique that has given rise in some quarters to a sharp distinction
between Viennese logical positivism and German logical empiricism, with the former accused of
reductionism and the latter praised for their anti-reductionism, a distinction which falsely discounts the
changing nature and variety of Vienna Circle doctrines. Reichenbach's defense of empiricism (1938)
turned on the replacement of the criterion of strict verifiability with one demanding only that the degree
of probability of meaningful statements be determinable. This involved opposition also to demands for
the eliminative reduction of non-observational to observational statements: both phenomenalism and
reductive physicalism were viewed as untenable and a correspondentist realism was advanced in their
stead. Now it is true that of the members of the Vienna Circle only Feigl ever showed sympathies for
scientific realism, but it is incorrect that all opposition to it in the Circle depended on the naive semantics
of early verificationism. Again, of course, some Vienna Circle positions were liable to Reichenbach's
criticism.
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Another misunderstanding to guard against is that the Vienna Circle's ongoing concern with
“foundational issues” and the “foundations of science” does in itself betoken foundationalism. (In the
Vienna Circle's days, such a view had it that the basic items of knowledge upon which all others
depended were independent of each other, concerned phenomenal states of affairs and were infallible;
nowadays, foundationalists drop phenomenalism and infallibility.) Already the manifesto sought to make
clear the Circle's opposition when it claimed that “the work of ‘philosophic’ or ‘foundational’
investigations remains important in accord with the scientific world conception. For the logical
clarification of scientific concepts, statements and methods liberates one from inhibiting prejudices.
Logical and epistemological analysis does not wish to set barriers to scientific enquiry; on the contrary,
analysis provides science with as complete a range of formal possibilities as is possible, from which to
select what best fits each empirical finding (example: non-Euclidean geometries and the theory of
relativity).” (Carnap-Hahn-Neurath 1929 [1973, 316]) This passage can be read as an early articulation of
the project of a critical-constructivist meta-theory of science that abjures a special authority of its own
beyond that stemming from the application of the methods of the empirical and formal sciences to science
itself, but instead remains open to what the actual practice of these sciences demands.
How then can Vienna Circle philosophy be absolved of reductionism? As noted, it is the Aufbau (and
echoes of it in the manifesto) that invites the charge of phenomenalist reductionism. Concerning this book
it has been argued that its strategy of reconstructing empirical knowledge from the position of
methodological solipsism (phenomenalism without its ontological commitments and some of its
epistemological ambitions) is owed not to foundationalist aims but to the ease by which this position
seemed to allow the demonstration of the interlocking and structural nature of our system of empirical
concepts, a system that exhibited unity and afforded objectivity, which was Carnap's main concern. (See
Friedman 1987, 1992, Richardson 1990, 1998, Ryckman 1991, Pincock 2000, 2003).
In fact, the Aufbau fails when it is read as a foundationalist project, as it was by Quine (1951a) who
pointed out that no eliminative definition of the relation ‘is at’ was provided (required for locating objects
of consciousness in physical space). But this did not prompt Carnap (1961a) to abandon as mistaken
reconstructions of the scientific language on the basis of methodological solipsism. Likewise, Carnap had
not been prompted do so some twenty years earlier by Neurath (1931b, 1932a) who argued that such a
type of rational reconstruction traded on objectionable counterfactual presuppositions (methodological
solipsism did not provide a correct description of the reasoning involved in cognitive commerce with the
world around us). All along Carnap (1932e, 1961a) merely conceded that it was more “convenient” to
reconstruct the language of science on a physicalistic basis. Carnap's responses are best interpreted, not as
clinging to lost epistemological foundations, but as indicating his overriding concern with explicative
language constructions of great variety and his long-standing and radical ontological abstemiousness.
(That Carnap in so responding also gave up on what he now considered an epistemology unduly
"entangled with psychological questions" (1934/37, §72) does not support the case for foundationalism
either, for already his earlier concern with different constructional systems speaks against it.)
Concerning physicalism likewise it must be asked whether the recognition of the irreducibility of
disposition terms, let alone of purely theoretical terms, spelt the end of that doctrine. By (1932e), Carnap's
physicalism was explicitly anti-foundationalist. That later in (1936/37) he called his non-eliminative
definitions of disposition terms “reduction sentences” indicates that it was enough for him to provide a
basis for the applicability of these terms by merely sufficient but not necessary conditions. Likewise,
Carnap's proposal (1939) to conceive of theoretical terms as defined by implicit definition in a noninterpreted language, but linked as a system via correspondence rules to terms for which a reductive chain
can be determined, suggest that what concerned him primarily was the capture of indicator relations to
sustain in principle testability of statements containing the terms in question. This is best understood as an
attempt to preserve the empirical applicability of the formal languages constructed by way of explication
for the contested concepts of scientific methodology, but not as reductivism with regard to some
foundational given.
By partial contrast, Neurath's own physicalism was fallibilist and anti-foundationalist from the start
(1931b, 1932a). Moreover, his on first sight obstruse conception of the form of protocol statements
(1932b) explicated the concept of observational evidence in terms that expressly reflected debts to
empirical assumptions which called for theoretical elaboration in turn. Unlike the logician of science
Carnap, who left it to psychology and brain science to determine more precisely what the class
observational predicates were that could feature in protocol statements (1936/37), the empirically oriented
meta-theoretician of science Neurath was concerned to encompass and comprehend the practical
22
complexities of reliance on scientific testimony (see Uebel 2005). In addition, Neurath's theory of
protocol statements also makes clear that his understanding of physicalism did not entail the eliminative
reduction of the phenomenon of intentionality but, like Carnap's logical behaviourist explications (1932c),
merely sought its integration into empiricist discourse.
Given these different emphases of their respective physicalisms, mention must also be made of the
significant differences between Carnap's and Neurath's conceptions of unified science: where the
formalist Carnap once preferred a hierarchical ordering of finitely axiomatized theoretical languages that
allowed at least partial cross-language definitions and derivations—these requirements were liberalized
over the years (1936b), (1938), (1939)—the pragmatist Neurath opted from the start to demand only the
interconnectability of predictions made in the different individual sciences (1935a), (1936c), (1944).
(Meterology, botany and sociology must be combinable to predict the consequences of a forest fire, say,
even though each may have its own autonomous theoretical vocabulary.) Here too it must be remembered
that, unlike Carnap, Neurath only rarely addressed issues in the formal logic of science but mainly
concerned himself with the partly contextually fixed pragmatics of science. (One exception is his 1935b, a
coda to his previous contributions to the socialist calculation debate with Ludwig von Mises and others.)
Not surprisingly, at times the priorities set by Neurath for the pragmatics of science seemed to conflict
with those of Carnap's logic of science. (These tensions often were palpable in the grand publication
project undertaken by Carnap and Neurath in conjunction with Morris, the International Encyclopedia of
the Unity of Science (Reisch 2003).) That said, however, note that Carnap's more hierarchical approach to
the unity of science also does not support the attribution of foundationalist ambitions.
The post-Aufbau Carnap thus fully represents the position of Vienna Circle anti-foundationalism. In this
he joined Neurath whose long-standing anti-foundationalism is evident from his famous simile likening
scientists to sailors who have to repair their boat without ever being able to pull into dry dock. Their
positions contrasted at least prima facie with that of Schlick (1934) who explicitly defended the idea of
foundations in the Circle's notorious debate over the form, content and status of scientific evidence
statements. Even Schlick conceded, however, that all scientific statements were fallible ones, so his
position remained less than wholly clear and different interpretation of it have been put forward. (On the
protocol sentence debate see, e.g., the differently centered accounts of Uebel 1992, Oberdan 1993, Cirera
1994.) While all in the Circle thus recognized as futile the attempt to restore certainty to scientific
knowledge claims, not all members embraced positions that rejected foundationalism tout court. Clearly,
however, attributing foundationalist ambitions to the Circle as a whole constitutes a total
misunderstanding of its internal dynamics and historical development, if it does not bespeak wilfull
ignorance. At most, a foundationalist faction around Schlick can be distinguished from the so-called left
wing whose members pioneered anti-foundationalism with regard to both the empirical and formal
sciences.
3.4 Scientific Theories, Theoretical Terms and the Problem of Realism
Yet even if it be conceded that the members of the Vienna Circle did not harbour reductionist ambitions,
the question remains open whether they were able to deal with the complexities of scientific theory
building.
Here the prominent role of Schlick must be mentioned, whose General Theory of Knowledge (1918,
second edition 1925) was one of the first publications by (future) members of the Vienna Circle to
introduce the so-called two-languages model of scientific theories. According to this model, scientific
theories comprised an observational part formulated with observational predicates as customarily
interpreted, in which observations and experiential laws were stated, and a theoretical part which
consisted of theoretical laws the terms of which were merely implicitly defined, namely, in terms of the
roles they played in the laws in which they figured. Both parts were connected in virtue of a correlation
that could be established between selected terms of the theoretical part and observational terms. In the
second half of the 1920s, however, Schlick's model, involving separate conceptual systems, was put aside
in favor of a more streamlined conception of scientific theories along lines as suggested by the Aufbau.
Clearly, however, Schlick's model represents an early form of the conception of scientific theories as
uninterpreted calculi connected to observation by potentially complicated correspondence rules that
Carnap reintroduced in (1939) and that became standard in the “received view”. (Another, albeit faint
precursor was the idea contained in a 1910 remark of Frank's pointing out the applicability of Hilbert's
23
method of implicit definition to the reconstruction empirical scientific theories as conceived, also along
the lines of two distinct languages, by the French conventionalists Rey and Duhem; see Uebel 2003.)
Even granted the model in outline, questions arise both concerning its observational base as well as its
theoretical superstructure. We already discussed one aspect of the former topic, the issue of protocols, in
the previous section; let's here turn to the latter topic. Talk of correspondence rules only masks the
problem that is raised by theoretical terms. One of the pressing issues concerns their so-called surplus
meaning over and above their observational consequences. This issue is closely related to the problem of
scientific realism: are there truth-evaluatable matters of fact for scientific theories beyond their empirical,
observational adequacy? Even though the moniker “neo-positivism” would seem to prescribe an easy
answer as to what the Vienna Circle's position was, it must be noted that just as there is no consensus
discernible today there was none in the Circle beyond certain basics that left the matter undecided.
All in the Vienna Circle followed Carnap's judgement in Pseudoproblems of Philosophy (1928b) and
Schlick's contention in his response to Planck's renewal of anti-Machian polemics (1932) that questions
like that of the reality of the external world were not well-formed ones but only constituted pseudoquestions. While this left the observables of empirical reality clearly in place, theoretical entities
remained problematical: were they really only computational fictions introduced for the ease with which
they they allowed complex predictive reasoning, as Frank (1932) held? This hardly seems to do justice to
the surplus meaning of theoretical terms over and above their computational utility: theories employing
them seem to tell us about non-observable features of the world. This indeed was Feigl's complaint (1950)
in what must count as the first of very few forays into “semantical realism” (scientific realism by another
word) by a former member of the Vienna Circle—and one that was quickly opposed by Frank's
instrumentalist rejoinder (1950). Carnap sought remain aloof on this as on other ontological questions. So
while in the heyday of the Vienna Circle itself the issue had not yet come into clear focus, by mid-century
one could distinguish amongst its surviving members both realists (Feigl) and anti-realists (Frank) as well
as ontological deflationists (Carnap).
Carnap's general recipe for avoiding undue commitments (while pursuing his investigations of various
language forms, including the intensional ones Quine frowned upon) was given in terms of the distinction
between so-called internal and external questions (1950a). Given the adoption of a logico-linguistic
framework, we can state the facts in accordance with what that framework allows us to say. Given any of
the languages of arithmetic, say, we can state as arithmetical fact whatever we can prove in them; to say
that accordingly there are numbers, however, is at best to express the fact that numbers are a basic
category of that framework (irrespective of whether they are logically derived from a still more basic
category). As to whether certain special types of numbers exist (in the deflated sense), that depends on the
expressive power of the framework at hand and on whether the relevant facts can be proven. Analogous
considerations apply to the existence of physical things (the external world) given the logico-linguistic
frameworks of everyday discourse and empirical science. (The near-tautologous nature of these
categorical claims in Carnap's hands echoes his earlier diagnosis of metaphysical claims as pseudostatements; see also 1934/37, Part V.A.) Unlike such internal questions, however, external questions,
questions whether numbers or electrons “really exist” irrespective of any framework, are ruled out as
illegitimate and meaningless. The only way in which sense could be given to them was to read them as
pragmatic questions concerned with the utility of talk about numbers or electrons, of adopting certain
frameworks. Carnap clearly retained his allegiance to the linguistic turn: existence claims remain the
province of science and there must be seen as mediated by the available conceptual tools of inquiry.
Logicians of science are in no position to double-guess the scientists in their own proper domain.
Matters came to a head with the discovery of a proof (see Craig 1956) that the theoretical terms of a
scientific theory are dispensible in the sense of it being possible to devise a functionally equivalent theory
that does not make use of them. Did this not rob theoretical terms of their distinctive role and so support
instrumentalism? The negative answer was twofold. As regards defending their utility, Carnap agreed
with Hempel (1958) that in practice theoretical terms were indispensible in facilitating inductive relations
between observational data. As regards the defense of their cognitive legitimacy, Carnap held that this
demanded determining what he called their “experiential import”, namely, determining what specifically
their empirical significance consisted in. It was for this purpose that Carnap came to employ Ramsey's
method of regimenting theoretical terms. Nowadays this so-called ramseyfication is often discussed as a
means for expressing a position of “structural realism”, a position midway between fully-blown scientific
realism and anti-realism and so sometimes thought to be of interest to Carnap. Let us consider Carnap's
own concern with ramseyfication concern in greater detail. Not only does the question of the viability of
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one of the Vienna Circle's most forward-looking stances in the debate about theoretical terms—intending
to avoid both realism and anti-realism—come to a head here, but also several other issues that bear on the
question of which, if any, forms of Vienna Circle philosophy remain viable.
Note that the issue of realism vis-à-vis theoretical terms is closely related to two other issues central to the
development of Vienna Circle philosophy: Carnap's further attempts to develop a criterion of empiricist
significance for the terms of the theoretical languages of science and his attempts to defend the distinction
between synthetic and analytic statements with regard to such theoretical languages.
In 1956 Carnap introduced a new criterion of significance specifically for theoretical terms (1956b). This
criterion was explicitly theory-relative. Roughly, Carnap first defined the concept of the “relative
significance” of a theoretical term. A term is relatively significant if and only if there exists a statement in
the theoretical language that contains it as the only non-logical term and from which, in conjunction with
another theoretical statement and the sets of theoretical postulates and correspondence rules, an
observational statement is derivable that is not derivable from that other theoretical statement and the sets
of theoretical postulates and correspondence rules alone. Then Carnap defined the “significance” of a
theoretical term in terms of it belonging to a sequence of such terms such that each is relatively
significant to the class of those terms that precede it in the sequence. Now those theoretical statements
were legitimate and cognitively significant that were well-formed and whose descriptive constants were
significant the sense just specified. It is clear that by the stepwise introduction of theoretical terms as
specified, Carnap sought to avoid the deleterious situations that rendered Ayer's criterion false (and his
own of 1928). Nevertheless, this proposal too was subjected to criticism (e.g., Rozeboom 1960, Kaplan
1975a). A common impression amongst philosophers appears to be that this criterion failed as well, but
this judgement is by no means universally shared (for the majority view see Glymour 1980, for a contrary
assessment see Sarkar 2001). Thus it has been argued that subject to some further refinements, Carnap's
proposal can be made to work—as long as the sharp distinction between observational and theoretical
terms can be sustained (Creath 1976). (In light of the objections to that distinction one wants to add: or by
a dichotemy of terms functionally equivalent to it.)
Carnap's own position on his 1956 criterion appears somewhat ambiguous. While he is reported to have
accepted one set of criticisms (Kaplan 1975b), he also asserted still after they had been put to him that he
thought his 1956 criterion remained adequate (1963b, §24b). Even so, Carnap there also advised
investigation of whether yet another, then entirely new approach to theoretical terms that he was
developing then would allow for an improved meaning criterion for them (ibid.). Yet when Carnap
offered the Ramsey method as a method of characterizing the “empirical meaning of theoretical terms” it
was not their empirical significance as such but the specific empirical import of theoretical terms that he
considered (1966, Ch. 26). What prompted him to undertake his investigations of the Ramsey method was
not dissatisfaction with his 1956 proposal as a criterion of significance for theoretical terms, but it was the
consequence that with its model of the theoretical language it proved impossible to draw the distinction
between synthetic and analytic statements in the theoretical language. The reason for this was that the
postulates for the theoretical language also specify factual relations between phenomena that fall under
the concepts that are implicitly defined by them. (As noted, a similar problem already had plagued
Carnap's analyses of disposition terms ever since he allowed for non-eliminative reduction chains.)
Carnap's attempt to address this problem by ramseyfication was published in several places from 1958
onwards. (See Carnap 1958, 1963, §24C-D and the popular exposition 1966, Chs. 26 and 28; compare
Ramsey 1929 and see Psillos 1999, Ch.3. This proposal and a variant of it (1961b) were both presented in
his 1959 Santa Barbara lecture (published in Psillos 2000a); as it happened, Kaplan presented his
criticism (1975a) of Carnap's 1956 criterion at the same conference.) With ramseyfication Carnap
adverted again to entire theories as the unit of assessment. Ramseyfication consists in the replacement of
the theoretical terms of a finitely axiomatized theory by bound higher-order variables. This involves
combining all the theoretical postulates (which define theoretical terms) and correspondence rules of a
theory (which link some of these theoretical terms with observational ones) in one long sentence and then
replacing all the theoretical predicates that occur in it by bound higher-order variables. This is the socalled Ramsey-sentence of the entire theory; in it no theoretical terms appear, but it possesses the same
explanatory and predictive power as the original theory: it has the same observational consequences.
However, Carnap stressed that the Ramsey sentence cannot be said to be expressed in a “simple” but only
an “extended” observational language, for due to its higher-order quantificational apparatus it includes
“an advanced complicated logic embracing virtually the whole of mathematics” (1966, [1996, 253]).
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Now, to distinguish between analytic and synthetic statements in the theoretical language Carnap made
the following proposal. Let the Ramsey sentence of the conjunction of all theoretical postulates (call this
T) and the conjunction of all correspondence rules of that theory (call this C) be considered as expressing
the entire factual, synthetic content of the scientific theory and its terms in their entirety (call this RTC).
As noted, in this Ramsey sentence all theoretical terms were replaced by higher-order variables; by
contrast, in the original conjunction of all theoretical postulates and all correspondence rules (call this TC)
the theoretical terms were left in place. Carnap now proposed that the statement “ RTC → TC” expressed
the purely analytic component of the theory, its “A-postulate” (or so-called Carnap sentence). But it
would be wrong to say that “RTC → TC” specified the meaning of these theoretical terms; rather, “the Apostulate states that if entities exist (referred to by the existential quantifiers of the Ramsey sentence) that
are of a kind bound together by all the relations expressed in the theoretical postulates of the theory and
that are related to observational entities by all the relations specified by the correspondence postulates of
the theory, then the theory itself is true.” Or differently put, the A-postulate “says only that if the world is
this way, then the theoretical terms must be understood as satisfying the theory” (1966 [1996, 271]).
Nevertheless, Carnap claimed to have separated the analytic and synthetic components of a scientific
theory.
Carnap intended Ramsey-style reconstructions of theories to save his formalist explicationist project and
allow the analytic/synthetic distinction to emerge unscathed from the criticisms of Tarski and Quine. Yet
Carnap's adoption of the Ramsey method met mainly with criticism (Psillos 1999, ch.3, 2000b,
Demopoulos 2003), even though ramseyfications continue to be discussed as a method of characterizing
theoretical terms (albeit with conditions not yet introduced by Carnap, as in Lewis 1970, Papineau 1996).
Here note, first, that the legitimation of theoretical terms by ramseyfication does not answer the realists'
original question: do electrons, say, really exist? For the Ramsey sentence of a theory to be true, it only
requires that, subject to the empirical constraints being met that are expressed in its observational part,
there exists some set of entities—whatever they are—that realizes the structure that its theoretical part
postulates. (Structural realists thus claim to be pursuing a middle way between realism and anti-realism.)
But note, second, that neither do we get the answer that what really exists is the structure that the
ramseyfication at hand identifies. Given the absence of a clause requiring unique realizability,
ramseyfications counseled modesty: the structure that is identified remains indeterminate to just that
degree to which theoretical terms remain incompletely interpreted (Carnap 1961b). To this we must add
that for Carnap ramseyfications of theoretical terms can support only internal existence claims: he
explicitly reaffirmed his confidence in the distinction between internal and external question to defuse the
realism/anti-realism issue (1966 [1996, 256]). This strongly suggests that with these proposals Carnap did
not intend to deviate from his deflationist approach to ontology. This is of some importance since
Carnap's turn to the Ramsey method might be interpreted as a turn to structural realism. (Here one may
ask whether structural realism is to be thought of as making internal or external existence claims. Since
the latter are at issue for structural realists, such an interpretation would appear to violate Carnap's
intentions.)
What must be considered, however, is that Carnap's proposal to reconstruct the contribution of theoretical
terms by ramseyfication falls foul of arguments deriving from M.H.A. Newman's objection to Russell's
structuralism in Analysis of Matter (see Demopoulos and Friedman 1985). This objection says that once
they are empirically adequate, ramseyfied theories are trivially true, given the nature of their
reconstruction of original theories. Russell held that “nothing but the structure of the external world is
known”. But if nothing is known about the generating relation that produces the structure, then the claim
that there exists such a structure is vacuous, Newman claimed. “Any collection of things can be organised
so as to have the structure W, provided there are the right number of them.” (Newman 1928, 144) To see
how this so-called cardinality constraint applies to ramseyfications of theories, note that in Carnap's hands,
the non-observational part of reconstructed theories, their theoretical entities, were represented by “purely
logico-mathematical entities, e.g. natural numbers, classes of such, classes of classes, etc.” Note also that
for him the Ramsey sentence asserted that “observable events in the world are such that there are numbers,
classes of such, etc., which are correlated with events in a prescribed way and which have among
themselves certain relations”, this being “clearly a factual statement about the world” (Carnap 1963b,
963). Carnap here had mathematical physics in mind where space-time points are represented by
quadruples of real numbers and physical properties like electrical charge-density or mass-density are
represented as functions of such quadruples of real numbers.
The problem that arises from this for Carnap is not so much the failure to single out the intended
interpretation of the theory: as noted, Carnap clearly thought it an advantage of the method that it
26
remained suitably indeterminate. The problem for Carnap is rather that, subject to its empirical adequacy,
the truth conditions of the Ramsey-sentences are fulfilled trivially on logico-mathematical grounds alone.
As he stated, Ramsey-sentences demand that there be a structure of entities that is correlated with
observable events in the way described. Yet given the amount of mathematics that went into the
ramseyfied theory—“virtually the whole of mathematics”—some such structure as demanded by the
Ramsey-sentence is bound to be found among those entities presupposed by its representational apparatus.
(The cardinality constraint is no constraint at all.) Irrespective of the issue of whether Carnap was a
structural realist or not, this consequence is grave indeed: reconstructed by ramseyfication, any theory is
trivially true for purely formal reasons (as long as it is empirically adequate). This consequence counts
against Carnap's proposal to use Ramsey sentences as reconstructions of the synthetic content of the
theoretical part of empirical scientific theories. Given the problem with (unrestricted) ramseyfications
generally is that “the truth of physical theory reduces to the truth of its observational consequences”
(Demopoulos and Friedman 1985, 635), this is a problem for Carnap independently of whether he devised
his ramseyfications with reductionist designs (which may be doubted) and independently of whether such
a reduction is ontologically inadequate (which would presuppose realism). What tells against Carnap's
project on its own terms is that ramseyfication trivializes the truth of physical theory in the manner
indicated: the empirical meaning of theoretical terms that Carnap sought to capture simply evaporates
(Demopoulos 2003).
This result casts its shadow over Carnap's last treatment of theoretical terms in its entirety and threatens
further consequences. If the reconstruction of empirical theories by ramseyfication in Carnap's fashion is
unacceptable, then all explications that build on this are called into question: explications of theoretical
analyticity as much as explications of the experiential import of theories. Given that no justice has been
done to the experiential import of theoretical terms, it seems clear that one must ask whether the analytic
components of a theoretical language have been correctly identified. If they have not, then the metatheoretical utility of the synthetic/analytic distinction is once again be called into question.
One is lead to wonder whether Carnap would not be well advised to return to his 1956 position. This
allowed for a criterion of empirical significance for theoretical terms but not for the analytic/synthetic
distinction to be sustained with regard to the theoretical language. According to Carnap's fall-back
position before he hit upon ramseyfication, it was thought possible to distinguish narrow logical truth
from factual truth in the theoretical language (1966, Ch. 28). Importantly, this would still allow useful
distinctions to be drawn in explication, like that of the status of the principles of metrical geometry in
special and in general relativity: while in the former they are logical truths, in the latter they are empirical
truths (Carnap 1934/37, §50; cf. Friedman 1993). Given that (minimally) synthetic statements can still be
built from exclusively logico-mathematical terminology due to implicit cardinality constraints (Ramsey's
example: every two things differ in at least thirty respects), what one would end up with, however, would
be the bare distinction between logical and descriptive terms (Demopoulos, personal communication).
The relative a priori framework of scientific theories accordingly would no longer be explained in terms
of (types of) statements but only in terms of vocabulary (plus formation and tranformation rules for the
language in question).
While it is difficult to silence the suspicion that an analytic/synthetic distinction that applies only to
observational languages—and admits inescapable semantical holism for theoretical languages—is not
what the debate between Carnap and Quine was meant to be all about, we should also recall our previous
findings. If Quine's objections to the analytic/synthetic distinction really spring ultimately from his
objection to the distinction between the logical and the factual, then Carnap's envisaged retreat here
would be less radical and his concesssion less wholesale than it would appear to be. While giving up on
the applicability of the wider concept of analyticity to theoretical languages, he would retain the basic
distinction between the logical and the factual. While the formalist project would thus be reduced in its
scope, it would by no means have ground to a halt altogether. (This presupposes, of course, that
specifying frameworks in terms of vocabulary throws up no insurmountable difficulties—and continues
to allow distinctions to be drawn as envisaged above—and that a version of Carnap's 1956 criterion of
significance for theoretical terms remains in the running.)
We are now in a position to return to a final criticism of the search for a criterion of empiricist
significance. Much has been made of the very status of the criterion itself (however it may be put in the
end): was it empirically testable? It is common to claim that it is not and therefore consign it to
insignificance in turn, following Putnam (1981a, 1981b). The question arises whether this is to overlook
that the criterion of significance was put forward not as an empirical claim but as a meta-theoretical
27
proposal for how to delimit empiricist languages from non-empiricist ones. Again, pursuing this line of
inquiry is not to deny that by some members of the Circle the meaning criterion may have been
understood in such a way that it became liable to charges of self-refutation. Even if that were the case, the
reason for this may be found not in the very idea of a meaning criterion, but in the contradictory status of
the Tractarian elucidations to which the criterion was likened. (Their legitimacy was at issue in debates
that divided the Circle in the early 1930s; see, e.g., Neurath 1932a.) Here primarily Carnap's
understanding will be considered, who from 1932 onwards put his philosophical theses in the form of
“proposals” for alternative language forms, but how the pragmatist alternative fares will also be
considered. Finally, we will consider where this does leave neopositivist anti-metaphysics.
For Carnap, the empiricist criterion of significance was an analytic principle, but in a very special sense.
As a convention, the criterion had the standing of an analytic statement, but it was not a formally
specifiable framework principle of the language Ln to which it pertained. Properly formulated, it was a
semantic principle concerning Ln that was statable only in its meta-language Ln+1. To argue that the
criterion itself is meaningless because it has no standing in Ln is to commit a category mistake, for metalinguistic assertions need not have counterparts in their object languages (Goldfarb 1997, Creath 2004,
Richardson 2004). Nor would it be correct to claim that the criterion hides circular reasoning, allegedly
because its rejection of the meaningless depends on an unquestioned notion of experiential fact as selfexplanatory (when such fact is still to be constituted). Importantly, Carnap's language constructor does
not start with fixed notions of what is empirical (rather than formal) or what is given (rather than assumed
or inferred), but from the beginning allows a plurality of perspectives on these distinctions (Ricketts
1994). Carnap's empiricist criterion of significance is precisely this: an explication, a proposal for how
empiricists may wish to speak. It is not an explanation of how meaning arises from what is not
meaningful in itself. Unlike theorists who wish to explain how meaning itself is constituted,
explicationists can remain untroubled by the regress of formal semantics with Tarskian strictures. For
them, the lack of formal closure (the incompleteness of arithmetic and the inapplicability of the truth
predicate to its own language) only betokens the fact that our very own home languages cannot ever be
fully explicated.
It may be wondered whether such considerations have not become pointless, given the troubles that
attempts to provide a criterion of significance ran into. However, even though the ramseyfication-based
criterion of significance now appears tainted, Carnap's 1956 criterion for constructed languages remains
in play. Moreover, there also remains the informal, pragmatic approach that can be applied even more
widely. Thus it is not without importance to see that pragmatic principles delineating empirical
significance (like Mach's or Quine's Peircean insight) are not ruled out from the start either. The reason
for this is different however. For pragmatists, the anti-metaphysical demarcation criterion is not strictly
speaking a meaning criterion. The pragmatic criterion of significance is expressly epistemic, not
semantic: it speaks of relevance with regard to an established cognitive practice, not in-principle truthevaluability. This criterion is most easily expressed as a conditional norm, alongside other methodological
maxims. (If you want your reasoning to be responsible to evidence, then avoid statements that experience
can neither confirm or disconfirm, however indirectly.) So the suggestion that the criterion of empirical
significance can be regarded as a proposal for how to treat the language of science cannot be brushed
aside but for the persistent neglect of the philosophical projects of Carnap or the non-formalist left Vienna
Circle.
Still, some readers may wonder whether in the course of responding to the various counter-criticisms, the
Vienna Circle's position has not shifted considerably. This indeed is true: the attempt to show
metaphysics strictly meaningless for once and all did not suceed. For even if Carnap's 1956 criterion and
the pragmatic approach work, they do not achieve that: Carnap's criterion only works for constructed
languages and the pragmatic one does not address the semantic issue. But it can be argued that while this
debilitates the Vienna Circle's most notorious claim, it does not debilitate their entire program. That was,
we recall, to defend Enlightenment reason and to counter the abuse of possibly empty but certainly illunderstood deep-sounding language in science and in public life. Their program was, to put it somewhat
anachronistically, to promote epistemic empowerment. This program would have been helped by an
across-the-board criterion to show metaphysics meaningless, but it can also proceed in its absence.
But now the suspicion may be that if all that is meant to be excluded is speculative reason without due
regard to empirical and logico-linguistic evidence, the program's success appears too easy. Few
contemporary philosophers would confess to such reckless practices. Still, even the rejection of
speculative reason is by no means uncontroversial, as shown by the unresolved status of the appeal to
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intuitions that characterizes much of contemporary analytical metaphysics and epistemology. Moreover,
much depends on what's considered to be “due regard”: is merely bad science “metaphysics”? Or only
appeals to the supernatural? And what about de re necessities? Or the seeming commitments of existential
quantification? The promotion of anti-metaphysics may be applauded in principle as an exercise in
intellectual hygiene, the objection goes, but in practice it excludes either too much or too little: it either
cripples our understanding of theoretical science or normalizes away the Vienna Circle's most notorious
claim.
In response it is helpful to consider the conception of metaphysics that can be seen to be motivating much
of the Circle's ethical non-cognitivism. What did Carnap (1935) and Neurath (1932a) dismiss when they
dismissed normative ethics as metaphysical and cognitively meaningless? One may concede that due to
the brusque way in which they put their broadly Humean point, they opened themselves to significant
criticism, but it is very important to see also what they did not do. Most notably, they did not dismiss as
meaningless all concern with how to live. Conditional prescriptions remained straight-forwardly truthevaluable in instrumental terms and so cognitively meaningful. In addition, their own active engagement
for Enlightenment values in public life showed that they took these matters very seriously themselves. (In
fact, their engagement as public intellectuals compares strikingly with that of most contemporary
philosophers of science.) But neither did they fall victim to the naturalistic fallacy nor were they simply
inconsistent. In the determination of basic values they rather saw acts of personal self-definition, but,
characteristically, Carnap showed a more individualistic and Neurath a more socially oriented approach to
the matter. What needs to be borne in mind, then, is the meaning that they attached to the epithet
“metaphysical” in this and other areas: the arrogation of unique and fully determined objective insight
into matters beyond scientific reason. It was in the ambition of providing such unconditional prescriptions
that they saw philosophical ethics being the heir of theology. (Compare Carnap 1935 and 1963b, §32 and
Neurath 1932a and 1944, §19.) Needless to say, it remains contentious to claim those types of
philosophical ethics to be cognitively meaningless that seek to derive determinate sets of codes from
some indisputable principle or other. But the ongoing discussion of non-cognitivism and its persistent
defense in analytical ethics suggest that, understood as outlined, the Circle's non-cognitivism was by no
means absurd or contradictory.
What may be taken from this is the idea to understand the left wing's anti-metaphysics as deflationist. As
philosophers they opposed all claims to have a categorically deeper insight into reality than either
empirical or formal science, such that philosophy would stand in judgement of these sciences as to their
reality content or that mere science would stand in need of philosophical interpretations. (Concerned with
practical problems, they likewise opposed philosophical claims to stand above the contestations of mere
mortals.) Importantly, such deflationism need not remain general and vague, but can be given precise
content. For instance, it has been argued (Carus 1999) that Carnap correctly did not understand Tarski's
theory of truth as a traditional correspondence theory such that truth consisted in some kind of agreement
of statements or judgements and facts or the world where the latter make true the former. In Carnap's
unchanged opposition to the classical correspondence theory of truth in turn lies not only the continuity
between his own syntactic and semantic phases, but also the key to his and the entire left Vienna Circle's
understanding of their anti-metaphysical campaign. (On various occasions in the early 30s, Hahn, Frank
and Neurath opposed correspondence truth very explicitly, while, in later years, Neurath resisted Tarskian
semantics precisely because he wrongly suspected it of resurrecting correspondentism and Frank
continued to castigate correspondentism whenever required. On this tangled issue, see Mormann 1999,
Uebel 2004, Mancosu forthcoming.)
This suggests that a hard core of Viennese anti-metaphysics survives the criticism and subsequent
watering down of the early claims made for their criteria of empirical significance, yet retains sufficient
philosophical teeth to remain of contemporary interest. The metaphysics which the left wing attacked,
besides the everyday supernaturalism and the supra-scientific essentialism of old, was the correspondence
conception of truth and associated realist conceptions of knowledge. These notions were deemed
attackable directly on epistemological grounds, without any diversion through the theory of meaning:
how could such correspondences or likenesses ever be established? As Neurath liked to put it (1930), we
cannot step outside of our thinking to see whether a correspondence obtains between what we think and
how the world is. (Against defenses of the correspondence theory by arguments from analogy it would
likewise be argued that it the analogy is overextended.)
Importantly, the left wing's deflationary anti-metaphysics was accompanied by a distinctively
constructivist attitude. (Here one must hasten to add, of course, that what was constructed were not the
29
objects of first-order discourse (tables, chairs, electrons and black holes) but the theoretical terms and
concepts needed for reflection about the cognitive enterprise of science (ideas like evidence and its
degrees and presuppositions).) As meta-theorists of science they developed explications: here the point is
that different types of explications can be envisaged, ranging from analytic definitions in terms of
necessary and sufficient conditions in formal languages all the way to pragmatic, exemplar-based criterial
delimitations of the central applications of contested concepts or practices. Two branches of the Circle's
constructivist tendency can thus be distinguished: Carnap's rational reconstructions and formalist
explications and Neurath's and Frank's empirically informed and practice-oriented reconceptualizations.
The difference between these formalist and naturalistic approaches can be understood as a division of
labor between the tasks of exploring logico-linguistic possibilities of conceptual reconstruction and
considering the efficacy of particular discursive practices. In principle, the constructivist tendency in
Vienna Circle philosophy was able to embrace both (compare Carnap 1934/37, §72 and Neurath 1936b;
cf. Uebel 2001). However, in their own day, this two-track approach remained unrealized as philosophical
relations between Carnap and Neurath soured over disputes stemming ultimately from both parties' failure
to recognize the potential compatibility.
Considering the Vienna Circle as a whole in the light of this reading of its anti-metaphysical philosophy,
we find the most striking division within it yet. Unlike Carnap and the left wing, Schlick had little
problem with a correspondence theory of truth once it was cleansed of psychologistic and intuitive
accretions and centered on the idea of unique coordination of statement and fact. In this lay the strongest
sense of continuity between his pre-Vienna Circle General Theory of Knowledge (1918/25) and his postTractarian epistemology (1935a, 1935b). (Schlick also showed little enthusiasm for the constructivist
tendencies which already the manifesto of 1929 had celebrated.) Allowing for some simplification, it
must be noted that Schlick's attack on metaphysics (which gradually weakened anyway) presupposes a
non-constructivist reading of the criterion of significance. Whether his conception can escape the charge
self-refutation must be left open here.
Much confusion exists concerning the Vienna Circle and history, that is, both concerning the Vienna
Circle's attitude towards the history of philosophy and science and concerning its own place in that
history. As more has been learnt about the history of the Vienna Circle itself—the development and
variety of its doctrines as well as its own prehistory as a philosophical forum—that confusion can be
addressed ever more conclusively.
As the unnamed villain of the opening sentences of Kuhn's influential Structure of Scientific Revolutions
(1962), logical empiricism is often accused of lacking historical consciousness and any sense of the
embedding of philosophy and science in the wider culture of the day. Again it can hardly be denied that
much logical empiricist philosophy, especially after World War II, was ahistorical in outlook and asocial
in its orientation. Reichenbach's distinction (1938) between the contexts of discovery and justification—
which echoed distinctions made since Kant (Hoyningen-Huene 1987) and was observed already by
Carnap in the Aufbau—was often employed to shield philosophy not only from contact with the sciences
as practiced but also culture at large. But this was not the case for the Vienna Circle at large. On the one
hand, unlike Reichenbach, who drew an oversharp break between the philosophy of old and the brave
new philosophy of his popular The Rise of Scientific Philosophy (1951), Schlick was very much
concerned to stress the remaining continuities with traditional philosophy and its cultural mission in his
last paper (1938). On the other hand, the left wing of the Circle tended to open scientific meta-theory to
the empirical sciences. To be sure, Carnap was happy to withdraw to the “icy slopes” of the logic of
science and showed no professional interest in the history of science or philosophy, let alone its social
history. Yet Neurath and Frank vigorously pursued the historical and practice-related sociological
questions that the pure logic of science had to leave unaddressed. (See, e.g., Neurath's studies of the
history of optics (1915, 1916), Frank's homage to Mach (1917), his pedagogical papers in (1949b) and his
concern with the practice of theory acceptance and change in (1956); cf. Uebel 2000 and Nemeth
forthcoming.) Moreover, it must be noted that Neurath all along had planned a volume on the history of
science for the International Encyclopedia of Science, a volume that in the end became Kuhn's Structure.
That is often held to be an ironical result, given how Kuhn's book is commonly read. But this is not only
to overlook that the surviving editors of that series, Carnap and Morris found little to object in it, but also
that Carnap found himself in positive agreement with what he had read (Reisch 1991, Irzik and Grunberg
1995; cf. Friedman 2001). Finally, one look at the 1929 manifesto shows that its authors were very aware
of and promoted the links between their philosophy of science and the socio-political and cultural issues
of the day.
30
Turning to the historical influences on the Vienna Circle itself, the scholarship of recent decades has
unearthed a much greater variety than was previously recognized. Scientifically, the strongest influences
belonged to the physicists Helmholtz, Mach and Boltzmann, the mathematicians Hilbert and Klein and
the logicians Frege and Russell; amongst contemporaries, Einstein was revered above all others. The
Circle's philosophical influences extend far beyond that of the British empiricists (especially Hume), to
include the French conventionalists Henri Poincaré, Pierre Duhem and Abel Rey, American pragmatists
like James and, in German-language philosophy, the Neo-Kantianism of both the Heidelberg and the
Marburg variety, even the early phenomenology of Husserl as well as the Austrian tradition of Bolzano's
logic and the Brentano school. (See Frank 1949a for the influence of the French conventionalists and the
existence of somewhat diffuse pragmatist sympathies; for the importance of Neo-Kantianism for Carnap,
see Friedman 1987, 1992, Sauer 1989 and Richardson 1998; for Neo-Kantianism in Schlick, see Coffa
1991, Ch. 9 and Gower 2000; for the significance of Husserl for Carnap, see Sarkar 2004 and Ryckman
forthcoming; the Bolzano-Brentano connection is explored in Haller 1986.) It is against this very wide
background of influences that the seminal force must be assessed that their contemporary Wittgenstein
exerted. The literature on the relation between Wittgenstein and the Vienna Circle is vast but very often
suffers from an over-simplified conception of the latter. (See Stern forthcoming for an attempt by a
Wittgenstein scholar to redress the balance.) Needless to say, different wings of the Circle show these
influences to different degrees. German Neo-Kantianism was important for Schlick and particularly so for
Carnap, whereas the Austrian naturalist-pragmatist influences were particularly strong on Hahn, Frank
and Neurath. Frege was of great importance for Carnap, less so for Hahn who looked to Russell for his
logical sophistication. Most importantly, by no means all members of the Vienna Circle sought to emulate
Wittgenstein—thus the division between the faction around Schlick and the so-called left wing of the
Circle.
These findings conclusively refute the picture long dominant due to A.J. Ayer's popularisation of the
Vienna Circle's doctrines. The picture suggested there of its philosophy is that of British empiricism
topped up with formal logic (Hume plus Tractatus); by contrast, the strong Neo-Kantian and post-Kantian
tendencies concerned with establishing the objectivity claim of science find no mention. In the preface to
his later anthology Logical Positivism, Ayer remarked that his own Language, Truth and Logic “did
something to popularize what may be called the classical position of the Vienna Circle” (1959, 8), but it
should be noted that Ayer's earlier book had made the connection between the Vienna Circle and British
empiricism wholly dominant. Misleadingly as regards the Circle's position, Ayer there (1936/46, 54, 96)
embraced Berkeley's epistemic phenomenalism and so adopted a traditional foundationalist position even
though he conceded fallibilist holism viz-a-vis hypotheses (any external world statement).
All that said by way of embedding the Vienna Circle's philosophy in its time, one must also ask whether
its members understood their own embedding correctly. Here one issue in particular is becoming
increasingly prominent and raises questions that are of importance for philosophy of science still today.
That is whether, after all, logical empiricism did have the resources to understand correctly the then
paradigm modern science, the general theory of relativity. According to the standard logical empiricist
story (Schlick 1915, 1917, 1921, 1922), their theory conclusively refuted the Kantian conception of the
synthetic a priori: Euclidean geometry was not only one geometry amongst many, it also was not the one
that characterized empirical reality. With one of its most prominent examplars refuted, the synthetic a
priori was deemed overthrown altogether. Thus Schlick convinced the young Reichenbach (1920) to drop
his residually Kantian talk of constitutive principles and speak of conventions instead (see Coffa 1991, ch.
10). What was not mentioned at all by Schlick were efforts by Neo-Kantians at the time, especially by
Ernst Cassirer (especially his 1921, developing themes from his 1910) to make do with a merely relative
a priori in helping along scientific self-reflection. Even though much later, and on the independent
grounds of quantum physics, Frank attested to the increased proximity of his and Cassirer's understanding
of scientific theories (1938), Schlick's negligence remains notable.
Most controversial is how the issue of general relativity as a touchstone for competing philosophies of
science was framed: having dismissed Kant's own synthetic a priori for its mistaken apodicity, no time
was spared for discussion of its then contemporary development in Neo-Kantianism as a merely relative
but still constitutive a priori. Now in the philosophy of physics, this omission—committed both by
Schlick and Reichenbach—has recently come back to haunt logical empiricists with considerable
vengeance. Thus it has been argued that the Schlick-Reichenbach reading of general relativity as
embodying the standard logical empiricist model of scientific theories, with high theory linked to its
observational strata by purely conventional coordinative definitions, is deeply mistaken in representing
the local metric of space-time not to be empirically but conventionally determined, as indeed it is special
31
relativity (Ryckman 1992) and that it is instead only the tradition of transcendental idealism that
possesses the resources to understand the achievements of mathematical physics (Ryckman 2005; cf.
Friedman 2001). It is tempting to speak of the return of the repressed Neo-Kantian opposition, but the
issue is sure to be joined by naturalistically inclined interpreters. Whatever the outcome, one can only
marvel at how on this issue the history of philosophy of science intersects with contemporary philosophy
of science.
In conclusion the dominant popular picture of the Vienna Circle as a monolithic group of simple-minded
verificationists who pursued a blandly reductivist philosophy with foundationalist ambitions is widely off
the mark. Instead, the Vienna Circle must be seen as a forum in which widely divergent ideas about how
empiricism can cope with modern empirical and formal science were discussed. While by no means all of
the philosophical initiatives started by members of the Vienna Circle have born fruit, it is neither the case
that all of them have remained fruitless. Nor is it the case that everything once distinctive of Vienna
Circle philosophy has to be discarded.
Consider verificationism. While the idea to show metaphysics once-and-for-all and across-the-board to be
not false but meaningless—arguably the most distinctive thesis associated with the Vienna Circle—did
indeed have to be abandoned, two elements of that program remain so far unrefuted. On the one hand, it
remains an open option to pursue the search for a criterion of empirical significance in terms of
constructed, formal languages further along the lines opened by Carnap with his theory-relative proposal
of 1956 (and its later defense against critics). On the other hand—albeit at the cost of merging with the
pragmatist tradition and losing the apparent Viennese distinctiveness—the option to neglect as
cognitively irrelevant, and in this sense metaphysical, all assertions whose truth or falsity would not make
a difference remains as open as it always was. In addition it must be noted that, properly formulated,
neither the formalist version of the criterion of empirical significance for constructed languages nor the
pragmatist version of the criterion for all languages are threatened by self-refutation.
Consider analyticity. Here again, the traditional idea—sometimes defended by some members—did show
itself indefensible, but this left Carnap's framework-relative interpretation of analyticity and the
understanding of the a priori as equally relative untouched. Still, given the misadventure of
ramseyfication, it must be conceded that the wide analytic/synthetic distinction cannot be upheld for the
theoretical languages of science. Conceived more narrowly, however, the distinction between framework
principles and content continues to be drawable in terms of the distinction between logical and empirical
truths (even allowing for flexibility in what may be considered a framework principle).
Consider reductionism and foundationalism. While it cannot be denied that various reductionist projects
were at one time or another undertaken by members of the Vienna Circle and that not all of its members
were epistemological anti-foundationalists either from the start or at the end, it is clearly false to paint all
of them with reductivist and/or foundationalist brushes. This is particularly true of the members of the socalled left wing of the Circle, all of whom ended up with anti-foundationalist and anti-reductionist
positions (even though this did involve instrumentalism for some).
Whether these results count as defeats of the original project depends at least in part on what precisely is
meant to be rejected when metaphysics is rejected and that in turn depends on what the positive vision for
philosophy consists in. Here again one must differentiate. While some ended with considerable more
sympathy for traditional philosophy than they displayed in the Circle's heyday, others stuck to their guns.
For them, what remained of philosophy stayed squarely in the deflationist vein established by the
linguistic turn. They offered explications of contested concepts or practices that, they hoped, would prove
useful. Importantly, the explications given can be of two sorts: the formal explications of the logic of
science by means of exemplary models of constructed languages, and the more informal explications of
the empirical theory of science given by spelling out how certain theoretical desiderata can be attained
more or less under practical constraints.
Readers will note that despite his enormous contribution to the development of Vienna Circle philosophy,
it is not Schlick's version of it that appears to this reviewer to be of continuing relevance to contemporary
philosophy—unlike, in their very different but ultimately not incompatible ways, Carnap's and Neurath's
(and Frank's). This may be taken as a partial endorsement of Hempel's 1991 judgement (quoted in sect. 1
above), against which, however, Carnap is here re-claimed for the Circle's left wing.
32
It would appear then that despite continued resistance to recent revisionist scholarship—consisting not so
much in contesting but in ignoring its results—the fortune of Vienna Circle philosophy has turned again.
Restored from the numerous distortions of its teachings that accrued over generations of acolytes and
opponents, the Vienna Circle is being recognized again as force of considerable philosophical
sophistication. Not only is it the case that its members profoundly influenced the actual development of
analytical philosophy of science with conceptual initiatives that, typically, were seen through to their
bitter end. It is also the case that some of its members offered proposals and suggested approaches that
were not taken up widely at the time (if at all), but that are relevant again today. Much like its precursors
Frege, Russell and Wittgenstein, the conventionalists Poincaré and Duhem, the pragmatists Peirce and
Dewey—and like its contemporaries from Reichenbach's Berlin group and the Warsaw-Lvov school of
logic to the Neo-Kantian Cassirer—the Vienna Circle affords a valuable vantage point on contemporary
philosophy of empirical and formal science.
Karl Popper, who died in 1994, was widely regarded as England's greatest philosopher of
science since Bertrand Russell. Indeed a philosopher of worldwide eminence. Today his
followers among philosophers of science are a diminishing minority, convinced that Popper's
vast reputation is enormously inflated. I agree. I believe that Popper's reputation was based
mainly on this persistent but misguided efforts to restate common-sense views in a novel
language that is rapidly becoming out of fashion. Consider Popper's best known claim: that
science does not proceed by "induction"—that is, by finding confirming instances of a conjecture
— but rather by falsifying bold, risky conjectures. Conformation, he argued, is slow and never
certain. By contrast, a falsification can be sudden and definitive. Moreover, it lies at the heart of
the scientific method.
A familiar example of falsification concerns the assertion that all crows are black. Every find of
another black crow obviously confirms the theory, but there is always the possibility that a nonblack crow will turn up. If this happens, the conjecture is instantly discredited. The more often a
conjecture passes efforts to falsify it, Popper maintained, the greater becomes its
"corroboration," although corroboration is also uncertain and can never be quantified by degree
of probability. Popper's critics insist that "corroboration" is a form of induction, and Popper has
simply sneaked induction in through a back door by giving it a new name. David Hume's famous
question was "How can induction be justified?" It can't be, said Popper, because there is no such
thing as induction!
There are many objections to this startling claim. One is that falsifications are much rarer in
science than searches for confirming instances. Astronomers look for signs of water on Mars.
They do not think they are making efforts to falsify the conjecture that Mars never had water.
Falsifications can be as fuzzy and elusive as confirmations. Einstein's first cosmological model
was a universe as static and unchanging as Aristotle's. Unfortunately, the gravity of suns would
make such a universe unstable. It would collapse. To prevent this, Einstein, out of thin air,
proposed the bold conjecture that the universe, on its pre-atomic level, harbored a mysterious,
undetected repulsive force he called the "cosmological constant." When it was discovered that
the universe is expanding, Einstein considered his conjecture falsified. Indeed, he called it "the
greatest blunder of my life." Today, his conjecture is back in favor as a way of explaining why
the universe seems to be expanding faster than it should. Astronomers are not trying to falsify it;
they are looking for confirmations.
Falsification may be based on faulty observation. A man who claims he saw a white crow could
be mistaken or even lying. As long as observation of black crows continue, it can be taken in two
ways; as confirmations of "all crows are black," or disconfirmations of "some crows are not
black." Popper recognized — but dismissed as unimportant — that every falsification of a
conjecture is simultaneously a confirmation of an opposite conjecture, and every conforming
instance of a conjecture is a falsification of an opposite conjecture.
Consider the current hypothesis that there is a quantum field called the Higgs field, with
its quantized particle. If a giant atom smasher some day, perhaps soon, detects a Higgs,
33
it will confirm the conjecture that the field exist. At the same time it will falsify the
opinion of some top physicists, Oxford's Roger Penrose for one, that there is no Higgs
field.
To scientists and philosophers outside the Popperian fold, science operates mainly by
induction (confirmation), and also and less often by disconfirmation (falsification). Its
language is almost always one of induction. If Popper bet on a certain horse to win a
race, and the horse won, you would not expect him to shout, "Great! My horse failed to
lose!"
Astronomers are now finding compelling evidence that smaller and smaller planets orbit distant
suns. Surely this is inductive evidence that there may be Earth-sized planets out there. Why
bother to say, as each new and smaller planet is discovered, that it tends to falsify the conjecture
that there are no small planets beyond our solar system? Why scratch your left ear with your
right hand? Astronomers are looking for small planets. They are not trying to refute a theory any
more than physicists are trying to refute the conjecture that there is no Higgs field. Scientists
seldom attempt to falsify. They are inductivists who seek positive conformations.
At the moment the widest of all speculations in physics is superstring theory. It conjectures that
all basic particles are different vibrations of extremely tiny loops of great tensile strength. No
superstring has yet been observed, but the theory has great explanatory power. Gravity, for
example, is implied as the simplest vibration of a superstring. Like prediction, explanation is an
important aspect of induction. Relativity, for instance, not only made rafts of successful
predictions but explained data previously unexplained. The same is true of quantum mechanics.
In both fields researchers used classical induction procedures. Few physicists say they are
looking for ways to falsify superstring theory. They are instead looking for confirmations. Ernest
Nagel, Columbia University's famous philosopher of science, in his Teleology Revisited and
Other Essays in the Philosophy and History of Science (1979), summed it up this way:
"[Popper's] conception of the role of falsification . . . is an oversimplification that is close to
being a caricature of scientific procedures."
For Popper, what his chief rival Rudolf Carnap called a "degree of confirmation"—a logical
relation between a conjecture and all relevant evidence—is a useless concept. Instead, as I said
earlier, the more tests for falsification a theory passes, the more it gains in "corroboration." It's as
if someone claimed that deduction doesn't exist, but of course statements can logically imply
other statements. Let's invent a new term for deduction, such as "justified inference." It's not so
much that Popper disagreed with Carnap and other inductivists as that he restated their views in
a bizarre and cumbersome terminology.
To Popper's credit he was, like Russell, and almost all philosophers, scientists, and ordinary
people, a thoroughgoing realist in the sense that he believed the universe, with all its intricate
and beautiful mathematical structures, was "out there," independent of our feeble minds, In no
way can the laws of science be likened to traffic regulations or fashions in dress that very with
time and place. Popper would have been appalled as Russell by the crazy views of today's social
constructivists and postmodernists, most of them French or American professors of literature
who know almost nothing about science.
Scholars unacquainted with the history of philosophy often credit popper for being the first to
point out that science, unlike math and logic, is never absolutely certain. It is always corrigible,
subject to perpetual modification. This notion of what the American philosopher Charles Peirce
called the "fallibilism" of science goes back to ancient Greek skeptics, and is taken for granted
by almost all later thinkers.
In Quantum Theory and the Schism in Physics (1982) Popper defends at length his "propensity
theory" of probability. A perfect die, when tossed, has the propensity to show each face with
equal probability. Basic particles, when measured, have a propensity to acquire, with specific
probabilities, such properties as position, momentum, spin and so on. Here again Popper is
introducing a new term which says nothing different from what can be better said in
conventional terminology.
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In my opinion Popper's most impressive work, certainly his best known, was his two-volume
The Open Society and Its Enemies (1945). Its central theme, that open democratic societies are
far superior to closed totalitarian regimes, especially Marxist ones, was hardly new, but Popper
defends it with powerful arguments and awesome erudition. In later books he attacks what he
calls "historicism," the belief that there are laws of historical change that enable one to predict
humanity's future. The future is unpredictable, Popper argued, because we have free wills. Like
William James, Popper was an indeterminist who saw history as a series of unforeseeable events.
In later years he liked to distinguish between what he called three "worlds"—the external
physical universe, the inner world of the mind, and the world of culture. Like Carnap and other
members of the Vienna Circle, he had no use for God or an afterlife.
Karl Raimund Popper was born in Vienna in 1902 where he was also educated. His parents were
Jewish, his father a wealthy attorney, his mother a pianist. For twenty years he was a professor
of logic and scientific method at the London School of Economics. In 1965 he was knighted by
the Crown.
I am convinced that Popper, a man of enormous egotism, was motivated by an intense jealousy
of Carnap. It seems that every time Carnap expressed an opinion, Popper felt compelled to come
forth with an opposing view, although it usually turned out to be the same as Carnap's but in
different language. Carnap once said that the distance between him and Popper was not
symmetrical. From Carnap to Popper it was small, but the other way around it appeared huge.
Popper actually believed that the movement known as logical positivism, of which Carnap was
leader, had expired because he, Popper, had single-handedly killed it!
By Hacohen's own account, Popper was a monster, a moral prig. He continually accused others
of plagiarism, but rarely acknowledged his own intellectual debts. He expected others to make
every sacrifice for him, but did little in return. In Hacohen's words, "He remained to the end a
spoiled child who threw temper tantrums when he did not get his way." Hacohen is ready to
excuse all this as the prerogative of genius. Those who think Popper a relatively minor figure are
likely to take a different view.
When Popper wrote "Logik der Forschung," he was barely thirty. Despite its flawed center, it
was full of good ideas, from perhaps the most brilliant of the bright young philosophers
associated with the Vienna Circle. But where the others continued to learn, develop and in time
exert a lasting influence on the philosophical tradition, Popper knew better. He refused to revise
his falsificationism, and so condemned himself to a lifetime in the service of a bad idea.
Popper's great and tireless efforts to expunge the word induction from scientific and
philosophical discourse has utterly failed. Except for a small but noisy group of British
Popperians, induction is just too firmly embedded in the way philosophers of science and even
ordinary people talk and think.
Confirming instances underlie our beliefs that the Sun will rise tomorrow, that dropped objects
will fall, that water will freeze and boil, and a million other events. It is hard to think of another
philosophical battle so decisively lost.
“Critical Rationalism” is the name Karl Popper (1902-1994) gave to a modest and self-critical rationalism.
He contrasted this view with “uncritical or comprehensive rationalism,” the received justificationist view
that only what can be proved by reason and/or experience should be accepted. Popper argued that
comprehensive rationalism cannot explain how proof is possible and that it leads to inconsistencies.
Critical rationalism today is the project of extending Popper’s approach to all areas of thought and action.
In each field the central task of critical rationalism is to replace allegedly justificatory methods with
critical ones.
Section 2 explains how critical rationalism arose out of the breakdown of Popper’s first justificationist
attempt to account for scientific progress. Section 2 also presents Popper’s first application of his nonjustificationist perspective to new fields in his The Open Society and Its Enemies. Section 3 first explains
Joseph Agassi’s view of the critical appraisal of metaphysical theories in scientific contexts as well as his
view of piecemeal rationality, and secondly portrays William Bartley’s more comprehensive view of non-
35
justificationism. Section 4 discusses Imré Lakatos’s extension of critical rationalism to mathematics.
Section 5 portrays Hans Albert’s systematic version of critical rationalism. His perspective incorporated
results of Popper, Agassi and Bartley and extended them to social and political theory. Section 6 suggests
that Mario Bunge’s fallibilism ─ which he developed independently of critical rationalists ─ is
sufficiently close to their views to count here: he develops critical tools for achieving progress without
justification in virtually all areas of thought. Section 7 discusses attempts to develop critical rationalism in
new and simpler ways. These views seek to do without frameworks and methodological rules; their
originators are Jagdish Hattiangadi, Gunnar Andersson, and David Miller. These theories deprive rational
thought of needed steering mechanisms. Section 8 presents the reintroduction of forms of justification
designed to be compatible with Popper’s criticism of induction. These have been developed by Alan
Musgrave, Volker Gadenne and John Watkins. Section 9 explains how Popper’s emphasis on the
importance of methodological rules in science has led to a critical rationalist sociology of science. The
main task of this sociology of science is to examine existing rules and methods as furthering or hindering
research. Section 10 calls attention to the alternative philosophical anthropology which Agassi has
proposed as a framework for critical rationalism. Whereas Popper saw rationality as contrary to human
nature’s craving for security, Agassi sees rationality as natural, but partial and improvable. Section 11
describes how Popper’s original political manifesto in The Open Society and Its Enemies has led to
attempts to use his arguments to defend both right-leaning and left-leaning political theories. Section 12
returns to Popper’s early researches in educational theory. His philosophy led to concerted efforts to
develop a new pedagogy which emphasizes active problem solving as the best learning method. This
pedagogy should promote autonomy and critical thinking. Section 13 concludes with the suggestion that
the success or the failure of the project of substituting critical for allegedly justificatory methods has still
to be judged.
Critical rationalism emerged from research by the Würzburg school of psychology. This school sought to
develop a deductivist philosophy of science to complement their deductivist psychology. While working
on this program, Karl Popper stumbled onto a non-justificationist theory of scientific knowledge: he
explained the growth of knowledge without proof. Non-justificationism, that is, the theory that no theory
can be proven, is at least as old as Socrates, but Popper’s version of it is the first that also purports to
explain the growth of knowledge. Popper and other critical rationalists took on the project of explaining
the growth of knowledge without justification. This project has produced various competing theories of
rationality and has been extended to many fields. This article will concentrate on the internal logic and
problems involved in the development of critical methods capable of producing the growth of knowledge.
Of the numerous justificationist predecessors let only this be said. The overwhelming majority of those
who comment on critical rationalism claim that critical rationalism is somehow incoherent and that
inductivism is better. A major exception was Bertrand Russell. He appreciated the logical strength of
critical rationalism and knew the logical weakness of induction. Nevertheless he clung to induction. He
thought that critical rationalism was a philosophy of despair. Whether his judgment of critical rationalism
was correct depends on whether its development can bring progress. To show this progress, new critical
rationalist ideas are described and presented below. This should provide an answer to Russell that he
amply deserves.
Inductive inferences have observations as premises and theories as conclusions. They are notoriously
invalid but often are deemed unavoidable. Critical rationalism views them as unnecessary. This point of
view grew gradually out of Karl Popper’s attempt to describe science without their use in Die beiden
Grundprobleme der Erkenntnistheorie (1932-33 ), where he still operated within the framework of
justificationism, that is, while viewing the aim of scientific method as the proper (justified) assessment of
the truth value of certain sentences. He hoped to build a theory of the proper assessment of sentences, that
is, of the possibility of proving the truth or falsity of some sentences. He began with the fact that a theory
is false if it contradicts a singular sentence describing some observation reports. Popper then said that
such singular sentences were veridical, that is, truthful as opposed to illusory, so they may be used to
produce final proofs of the falsity of some universal sentences. For example, the singular sentence, “That
swan is black,” if it is a true report of some observation, can be used to produce a final proof of the falsity
of the universal sentence, “All swans are white.” But, he argued, proof of universal sentences or the
demonstration that they are probable requires inductive inferences. As a consequence no such putative
proof can be valid.
Popper himself found the theory he presented in Die beiden Grundprobleme der Erkenntnistheorie
without chapter 5 inadequate for three reasons. The first reason is that singular statements are not
36
veridical. He began work on this problem in chapter 5 of Die beiden Grundprobleme. This chapter
contains a theory of science which differs on important points from the theory found in the rest of that
volume. The second reason that Popper’s first attempt broke down is that one can circumvent refutations
by ad hoc stratagems, as Hans Reichenbach quickly pointed out in a note which responded to Popper’s
first publication of his view in Erkenntnis. The third reason was Popper’s inability to handle the problem
of the demarcation of science from non-science with his idea that we show how science properly assigns
truth values to sentences with no inductive inference. On a justificationist theory of the task of the
philosophy of science such as Reichenbach’s, which was identical to Popper’s theory as he wrote Die
beiden Grundprobleme without chapter 5, science should be demarcated by the proper assignment of truth
values: science is the set of sentences with justifiably assigned truth values. The task of the philosophy of
science is to explain how these assignments are properly made. (Reichenbach said the calculus of
probabilities serves that purpose.) Popper argued that it is not possible to properly assign either the truth
value True or some degree of probability to universal sentences. He called such sentences “fictions”,
which is a term he had earlier taken over from Hans Vaihinger. On the theory presented in Die beiden
Grundprobleme without chapter 5, after science had done its job, there were still, on the one hand, some
fictions which ought to be deemed scientific such as the theories of the Würzburg school in psychology
and, perhaps, as he said later, Einstein’s physics, and, on the other hand, other fictions which should be
deemed unscientific, such as the psychologies of Freud and Adler. He could not distinguish between these
two sets of theories within his justificationist framework, since, on this view, only proofs or refutations of
these theories could do that. He asserted, however, that no proof was possible and refutations could
establish only the falsity of universal propositions.
As a consequence of these three difficulties Popper developed an entirely different theory of science in
chapter 5, then in Logik der Forschung. In order to overcome the problems his first view faced, he
adopted two central strategies. First, he reformulated the task of the philosophy of science. Rather than
presenting scientific method as a tool for properly assigning truth values to sentences, he presented rules
of scientific method as conducive to the growth of knowledge. Apparently he still held that only proven
or refuted sentences could take truth values. But this view is incompatible with his new philosophy of
science as it appears in his Logik der Forschung: there he had to presume that some non-refuted theories
took truth values, that is, that they are true or false as the case may be, even though they have been neither
proved nor refuted. It is the job of scientists to discover their falsity when they can. So, he worked around
the difficulty posed by the fact that, on the one hand, he had to assume that theories were refutable and
thus had truth values, whereas, on the other hand, he thought that only proven or refuted theories had truth
values at all. He argued that his view could be interpreted as realist or as antirealist. He hedged his bets as
best he could and appealed to Mach, who had stipulated that one should avoid participation in any
metaphysical dispute.
In Logik der Forschung Popper solved his three initial difficulties in the following ways. First, instead of
claiming that singular sentences were veridical, he said that basic statements are only provisionally
accepted, provided that they were repeatable and so testable. He thereby introduced the following rule:
consider only repeatable basic statements. He claimed that the provisional acceptance of basic statements
does not disqualify them as refutations of theories—no longer simply universal sentences—because for
the most part we can agree on which basic sentences we provisionally assume to be true. Second, he
proposed the rule that one should always replace some theory which is contradicted by a basic statement
by whichever new alternative has the highest degree of falsifiability. This rule should guarantee that
refutations lead to progress. Reichenbach had declared that there was no logic of scientific method, that is,
no proof or refutation. The basis for his claim that there could be no refutation was that any theory could
be protected from a putative refutation with some ad hoc maneuver. Popper responded to Reichenbach
with his Logik der Forschung (Logic of Research) and by introducing methodology into his deliberations.
The methodological rule enabled him to avoid ad hoc protection of theories and thus enabled him to show
how theories could be refuted. Third, he introduced the rule: only refutable theories—the term “fiction”
no longer appears in his work—are scientific and may be deemed scientific.
This view was no longer justificationist, that is, it no longer claimed properly to assign truth values to
sentences. All “assignments” are conjectural. But Popper had at that point no non-justificationist theory of
rationality in general; his theory applied to science alone. He did not at that point notice problems which
his theory raised for the broader framework of rationality which all philosophers of science had used
since antiquity, the framework that identified the rational with the proven.
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The conflict between Popper’s new theory of science and his older theory that only proven or refuted
sentences can take truth values was removed by Tarski. Tarski’s definition of truth, as Tarski explained to
Popper, allows for non-proven but still true sentences. Tarski thereby did away with the theory of truth
that had given Popper so much trouble. Tarski did not necessarily offer Popper an adequate theory of
truth for his philosophy of science. But Tarski did free him from a false theory which was a great
impediment to the construction of a truly fallibilist, realist theory of science. Popper never clearly
explained the importance that Tarski had for him at the time. This failure to explain how the logic of his
problem changed as a result of Tarski’s theory was part of his repression of the fact that he had held a
justificationist theory of truth for a long time, even after he began writing a fallibilist book. After his
meeting with Tarski, he was free to develop his fallibilist theory of science in new ways, because he could
claim that theories could be true even though there was no proof of them. During his earlier years in
London, during 1946-1965 or so, he returned to the possibilities this fact opened up.
In Logik der Forschung Popper developed a theory of the growth of scientific knowledge without
justification. But he had no general theory of rationality without justification. Indeed, he still limited
rationality to science and methodology. However, at least three problems arose for this limited view of
rationality.
Popper maintained at that point that scientists gain knowledge not by proofs but by refutations of good
conjectures and by replacing them with new and better ones. These new conjectures avoid earlier
mistakes, explain more, and invite new tests. He originally thought of this theory as eo ipso a theory of
rationality: outside of science and methodology he made no allowance for rationality. He identified
research, science and methodology, as the title of his book indicates.
Difficulties piled up fast. First, if rationality is limited to science, how is methodology rational?
Methodology can only be rational if methodology is the empirical study of science—as Whewell said—or
if non-empirical research can be rational. Popper could not view methodology as a science of science
because he held that it is not merely descriptive but also prescriptive. Yet it should be rational.
The second problem arose as Popper tried to apply his methodology of the physical sciences to the social
sciences. The Poverty of Historicism and The Open Society and Its Enemies defend the open society on
the grounds that only open societies preserve reason, that is, criticism, and as a consequence only open
societies can be civilized. But why is a choice for the open society rational? He had no answer. He merely
said that the acceptance of reason was a consequence of sympathy for others. Nothing can be said to
convince those to change their minds who accept the barbaric consequences of fascism or communism.
The third problem concerns metaphysics. Before he had ever developed his own philosophy of science, he
had defended in his doctoral dissertation the view that metaphysical hypotheses can serve as working
hypotheses in the construction of scientific theories. His discussion there merely concerned the use of
physicalist metaphysics as a guide for psychological research. He said that this was fine, but one should
not decide a priori that a view of psychological processes as physical is needed or even possible.
Scientific research—he was not clear then what that meant—should decide this. He was later pressed,
however, to decide between competing metaphysical theories with which to interpret science, even in the
absence of a scientific answer. Was the world determined or not? Questions such as this raised the
question as to whether one metaphysical theory can be better or worse than another and whether one
could find out which one is better. He gave up his earlier view of rationality as limited to scientific
research and methodology, but he still insisted that for science some metaphysical theories are merely
heuristic, and no more than that.
To extend his theory that rationality consisted of scientific research and methodology alone, Popper
loosened his standard of rationality. Rejecting the older standard of rationality — proof – - as too high, he
began to view the standard for science, refutability, as too high for the rationality that obtains outside
science. Whereas earlier he had replaced justification with refutation, he now replaced refutation with
criticism. Popper thereby created a new philosophical perspective by generalizing his theory of scientific
research. The name he gave to this extension is “critical rationalism.” Popper introduced it in the
introduction to his Conjectures and Refutations, where he characterized it briefly as the critical attitude.
He used it also to describe views he developed earlier, in The Open Society and Its Enemies.
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Could his critical rationalism apply to other fields? Could various fields also not only do without
(epistemological) justification but also raise their levels of rationality with the use of critical methods?
Critical rationalism became a project to employ critical methods as a substitute for epistemological
justification in all areas of life.
Outside of Popper’s own efforts to develop this project, the first two most significant endeavors were
undertaken by Joseph Agassi and William Bartley. Although Agassi’s efforts began somewhat earlier
than Bartley’s, their development overlaps considerably; the two were in conversation with each other for
much of the time that they were working out their ideas as Popper’s students. I begin with Agassi, who
developed Popper’s philosophy piecemeal and then turn to Bartley who attempted to give critical
rationalism a comprehensive statement, that is, a version of it which would explain how a critical
rationalist could adopt a critical stance toward any idea whatsoever, including its own claims.
Agassi began with his dissertation, in which he posed the question, How can metaphysics be used to
guide scientific research without making science subordinate to it? Duhem had warned that, were science
to concern itself with metaphysics, it would be subordinate to it. Encouraging scientists to engage in
metaphysical debates would cause dissent and lead them away from science’s main task of constructing
empirical theories.
Agassi’s project was to show how metaphysical research could facilitate empirical progress without
tyrannizing science. He did this by extending Popper’s theory of the methods of scientific practice to
include the critical, and thereby progressive, use of metaphysical theories to guide scientific research. On
his view metaphysics need not be a mere heuristic, that is, a source of ideas, but rather a systematic guide
to scientific research and a provisional standard for desirable theories. Metaphysics can be useful in
advancing science by giving guidelines for the search for empirical explanations and by deepening the
understanding of the world offered by science. But, he also said, it can help achieve these aims only when
used critically. A critical stance toward metaphysics is possible when two or more metaphysical research
programs compete with each other to construct empirically refutable theories. This, he argued, is just
what happened when Faraday used his metaphysical field theory as the framework within which he
constructed physical (field) theories. His competitors tried to explain the same phenomena under the
Newtonian assumption that all forces act at a distance. Faraday’s theory of electro-magnetic events
eventually had an enormous impact, because his metaphysics enabled him to construct better physical
theories than his competitors.
Bartley developed a comprehensive version of critical rationalism. He argued that there were two
problems that showed Popper’s original version was too limited. Popper encountered the first of these as
he wrote The Open Society and Its Enemies where he discussed the problem: Why should one be rational?
He conceded that rationality is limited, as its choice is pre-rational, a decision based on feelings. Bartley
viewed Popper’s problem of the limits of the ability to argue rationally in favor of rationality as parallel to
a problem he (Bartley) had earlier encountered in religious philosophy: defenders of religion claim that
commitment to some religion is just as rational as commitment to rationality: each individual has to
choose some starting point, and each starting point must be arbitrary. Each starting point then is just as
pre-rational as the other, since each choice is beyond the limits of reason.
Bartley viewed the inability to defend rationality rationally as amounting to the inability to show the
superiority of rational methods to solve problems over any other method. Bartley saw this limitation as an
important defect. But in Popper’s approach to rationality as critical rather than justificatory, he found a
way to overcome it. For, he argued, on the one hand, the theory of rationality as proof should itself be
proven, but in fact it is not provable, whereas, on the other hand, the theory of rationality as readiness to
appraise theories critically should itself be open to criticism, and this is quite possible. It is then no longer
the case that the adoption of a rational approach to problems is no more rational than commitments to
belief systems, such as those of some religion: the theory that rational practice means holding all theories
open to criticism, may itself be held open to criticism. This also means that the use of rational methods to
solve problems may be rationally defended, that is, we may use rationality to answer objections to the use
of rationality.
Could this theory allow one to hold religious beliefs rationally by holding them open to criticism? Bartley
never answered this question explicitly. He hinted that he did believe this was the case, and some have
understood him as adopting this position. Some critical rationalists are believers and some are not.
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Standards here remain vague. The winner of the Popper essay prize argued that Christians were also
critical rationalists, because they discussed, for example, the theological significance of their religious
experiences and have developed their views at Church councils. (Elliot 2004) Agassi has pointed out that
the Talmudic tradition is highly critical within certain bounds, yet cannot be said to have a high degree of
rationality. If all critical discussions, even those within sects, qualify their practitioners as critical
rationalists, then critical rationalism itself dissolves. To take seriously the replacement of justification
with criticism, Agassi suggests, requires demarcation between effective and ineffective critical methods.
Bartley called his view “comprehensively critical rationalism” to distinguish it from Popper’s critical
rationalism. It should not merely explain how one can conduct rational inquires in specific fields, but it
should apply to the theory of rationality itself. Bartley added a list of critical standards one may use to
evaluate ideas in any area whatsoever: a proposed idea should be a solution to an important problem,
internally consistent, not refuted, and consistent with science. The first three are incorporated into
virtually all critical rationalist theories. The fourth has been treated with more caution: science might also
be mistaken, especially when it contains competing theories. A new metaphysical alternative may be
inconsistent with established physical theory, as Faraday’s was, yet be quite important for progress.
John Watkins considered Bartley’s theory a reinforced dogmatism with a “Heads I win, tails you lose”
strategy: If comprehensive critical rationalism faces no effective criticism it wins, but if it does, it thereby
shows that it can meet its own standards and then again it wins. This criticism overlooks the fact that, if it
faces effective criticism, it is shown to be wrong. Bartley’s standard is a necessary condition of rationality,
but meeting it is no reason for clinging to an effectively criticized theory.
Bartley’s ideal of holding all ideas open to criticism has been an important part of critical rationalism. But
it soon became apparent that the problems of how to develop critical rationalism were more important
than demonstrating just how comprehensive it could be or of maintaining this comprehensive position. In
order to see how and why this realization came about it is useful to return to Agassi.
Agassi deems the focus of Bartley’s of approach to be misplaced: it unduly emphasizes the defense of
rationality as rationally defensible. Rationality does not need defense; it needs improvement, Agassi says.
And we may try to improve it piecemeal. We are all rational to some degree and are all interested from
time to time in using reason more effectively than we now do. We cannot help but be rational, since
thinking is, like seeing, innate to some extent. No one is always rational or perfectly rational any time.
Our best hope, then, is to use rationality to improve the partial and limited rationality which we all use to
one degree or another. We use a bootstrap process in that we use the rational methods we now have at
hand to develop better methods, whereby the methods we use may very well be corrected or even
discarded.
Agassi also applied Popper’s non-justificationism to the historiography of science. Like many, Popper
wanted the theory of science to describe science, but he hardly tried to apply his view to the history of
science. Agassi developed a far wider picture of the history of science from Popper’s viewpoint,
contrasting the traditional inductivist and conventionalist historiographies with a non-justificationist one.
Inductivism distorts the history of science as it is the view of innovations as either completely right or
quite useless; conventionalism distorts the history of science because it explains away radical changes.
John Wettersten extended this application to the historiography of psychology, explaining how a nonjustificationist approach was needed to remove peculiar distortions there.
In Proofs and Refutations Imré Lakatos extended the range of critical rationalism into mathematics. This
area is just where one would expect that it would be the most difficult to develop a theory of the growth
of knowledge by criticism rather than by proof, or, as Lakatos put it, by proofs and refutations. Putative
counter-examples, he illustrated historically, often refute “proofs” and thus require improvements.
Lakatos did not provide for the use of frameworks to formulate problems in mathematics, nor did he
discuss the rules which mathematicians should follow in formulating and criticizing proofs. He forcefully
argued against premature formalization, but he did not allow for the modern method of introducing a field
axiomatically from the start. His theory of response to criticism only shows that varying ways of
responding to problematical cases are available.
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As a beginning this is fine. But caring for the central task of critical rationalism, that is, for the
development of critical methods (in mathematics) as an alternative to the quest for justifications, requires
the replacement of justificationist methods with critical ones. Is this at all possible? Answers to this
question might enlighten us about the rationality of mathematical research. They might supplement and/or
improve Lakatos’s portrayal of mathematical research by accounts of the ways it proceeds, and explain
how decisions about the direction of research are made rationally.
Several thinkers have taken up this question; but with only one exception, they have sought to use
Lakatos’s justificationist methodology of scientific research programs. The exception is Peggy Marchi
who broke off her research before she had constructed any developed view. Three thinkers, however,
have made attempts to take Lakatos’ methodology of research programs in a critical spirit and then apply
it to the history of mathematics.
D.D. Spalt (Spalt 1981) argues that Lakatos’ methodology of research programs is inapplicable to the
history of mathematics as mathematicians are more open skeptical and critical than Lakatos’ methodology
describes. This confirms Lakatos’s turn away from a critical approach, but does not help us further since
it does not go on to ask if a genuinely critical approach, say, to the use of research programs such as
Agassi’s would help us. But Spalt also finds no mathematicians who follow any clear research program at
all. He defends a view of mathematics which has great similarity to Feyerabend’s view of science: there is
no methodology which can describe all mathematical research.
G. Giorello (Giorello 1981) argues that Lakatos’ theory of scientific research programs is better
applicable to mathematical research than Popper’s or Kuhn’s. Teun Koetsier in turn found Giorello’s
argument inadequate (Koetsier 1991 pp. 145ff.). This is not surprising, since Lakatos’ methodology of
research programs is sketchy.
Koetsier was not satisfied with Giorello’s vague results nor with Spalt’s negative ones. He proposed a
revision of Lakatos’ theory which would enable him to describe how mathematical research proceeds. His
revised version is closer to Agassi’s theory of research programs, which, Agassi suggested, might be used
to explain how mathematical problems were chosen and how mathematical research was coordinated.
Lakatos’s historical reconstructions of mathematical developments are Popperian in that they portray not
only mathematical theorems and their proofs, but also their refutations, and their replacement by new
ones. Koetsier criticizes this portrayal. He finds instead that the aim of mathematical research has been
directed at refining mathematical theorems. The refined theorems are then by and large accepted and
entered into the body of mathematical knowledge, where they then stay, subject only to further
refinements. Koetsier agrees, however, that Lakatos’s theory does show how mathematicians work when
solving problems within some narrowly defined areas of research. This research is fallible, he agrees, and
this allows it to progress by the discovery of difficulties with previous theories which are overcome by
succeeding ones.
Koetsier discusses clusters of mathematical theories that are part of identifiable research traditions. These
traditions pose their own problems and are identifiable by their offerings of clusters of mathematical
theorems. Each tradition, however, is not replaced by some competing one as in the case of science,
where one explanation is superseded by another leading to the rejection of the former. In this respect the
theories of science of Popper and/or Lakatos cannot be applied to the history of mathematics. Rather,
each theory progresses in its domain and the results it produces are largely cumulative.
In order to explain how progress is made in such research traditions, Koetsier employs the suggestion
made by Marchi that theorems should be taken as analogous to facts. (Marchi 1976) Whereas scientists
seek to explain facts, mathematicians seek to prove theorems. Theorems are, just as facts, accepted
provisionally. Instead of seeking to explain them as in science, mathematicians seek to prove them.
Mathematics grows as new theorems are discovered and proved.
This theory leads back to the problem posed by Agassi and Marchi: How is research coordinated?
Koetsier finds that Lakatos’s theory of mathematics describes “local” mathematical research rather well.
It describes how they solve problems within some cluster of theories and/or methods. He finds various
research traditions, which have been used to set problems. But, he does not explain how such traditions
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arise nor why they are chosen. Mathematical research is, then, coordinated by interests in particular kinds
of mathematical objects and/or particular methods. But, how are these chosen? Why do they change?
Koetsier also faces the question: Which theorems should mathematicians prove and why? He notes that
some are central and others that seem simply too ad hoc to bother with. But, how does one decide? He
offers a list of measures by which to judge the importance of theorems. His list of methods for appraising
the ad hoc nature of theorems is interesting but still rather ad hoc. (Koetsier p. 170-171)
Agassi’s theory of metaphysical research programs might have helped him here. Unlike Lakatos’ inferior
and subsequent theory, Agassi’s was designed to solve the problems of “How is scientific research
coordinated?” or “How do scientists choose their problems?” and “How can we explain simultaneous
discoveries?” His answer is that problems in science are often chosen for their relevance to metaphysical
problems. He developed at some length and in some depth the conflict between Faraday’s field theory and
Newton’s atomic theory to show how problems were chosen which bore on this controversy and how the
two metaphysical research programs could compete against each other.
How much of the choice of problems in the history of mathematics can be explained by Agassi’s
conjecture that they are regularly chosen due to their relevance to metaphysical problems? This is still an
open question. But some problems clearly were. Among them are problems concerning irrational numbers,
whether numbers exist in a Platonic world, problems concerning the nature of infinitesimals or irrational
numbers or the square root of minus one or the nature of transfinite numbers as well as questions
concerning the possibilities of non-Euclidean geometries. A history of mathematics written from this
point of view might be enlightening, if it could portray underlying metaphysical concerns as focusing
mathematical research on certain kinds of problems and the development of methods to deal with them.
It should be noted that J. O. Wisdom had portrayed the development of the calculus as a response to the
criticisms of Berkeley before Lakatos began his research (Wisdom 1939; 1941). His view is less radical
than Lakatos’s however, since Lakatos, but not Wisdom, said that the growth of mathematical knowledge
by proofs and refutations continues even after the introduction of new formal methods of logic. The
formal proofs in the logical language are indeed, Lakatos says, immune from refutations, but the
translations from the mathematical into the logical language are always open to question.
In the 1960s, Hans Albert began to apply critical rationalism to social and political theory. His writings
have become the standard statement of critical rationalism in the German-speaking world, if not
elsewhere. He argues that any attempt at justification faces a three-pronged difficulty that is traceable to
Agrippa: One alternative leads to an infinite regress as one seeks to prove one assumption but then needs
to assume some new one; a second alternative lands in a circular argument as one assumes what one seeks
to prove; a third alternative takes some arbitrary starting point and holds to it dogmatically. Outside of
these three unacceptable moves, justificationism offers no other alternative. Since none of these three
alternatives provide any justification at all, we should abandon the quest for justification. Instead we
should hold all theories open to criticism, as Popper and Bartley have proposed. He takes over Agassi’s
theory of research programs, but, due to his emphasis on the comprehensive nature of critical rationalism,
tends to side with Bartley more than Agassi on questions of rationality. He has never, however, had any
open dispute with Popper, Bartley or Agassi even though the three thinkers disagree on various
significant points. He builds what he can from their points of view into his own version and avoids
controversial issues among critical rationalists, while developing polemics against its detractors.
His major project is to explain how the theory of rationality proposed by Popper, Bartley and Agassi is, or
can be made to be, applicable to virtually all areas of human endeavor—ethics, politics, social science,
science, and so forth. He has from time to time presented this as an alternative to the so-called Frankfurt
School that was especially influential in Germany in the late 60s and 70s. Its members thought themselves
capable of deep analyses of society to show what went wrong in German history—why, for example,
Germany was authoritarian. Members of this school berated alternatives such as Albert’s as “positivist,”
by which they seemed to have meant that it did not take into account the human dimensions of imperfect
institutions. Because it looked at them too narrowly from an empirical, technical perspective it passed
over too quickly the unhappy consequences they have. Albert countered that the failure to separate
descriptive and prescriptive questions leads to the failure of the Frankfurt School to draw a realistic
picture of society and such a picture is the necessary foundation for any adequate theory of social reform,
which critical rationalism by no means opposes. It attempts rather to make it realistic. The political ideas
42
of critical rationalism as presented by Popper and by Albert were the most popular in Germany next to
those of the Frankfurt School. Albert also presented critical rationalism as superior to the hermeneutic
theories of Hans-Otto Apel and Hans Georg Gadamer.
Albert has dealt extensively with methodology in economics, criticizing neo-classical economics for its
unrealistic assumptions about the rationality of human actions, and its presumptions that there can be a
measure of the social welfare of society. But he views the tradition of neoclassical economics as the best
that the social sciences have to offer. He hopes to reform it by making its psychological assumptions
more realistic. Here he decidedly parts company with Popper, who is far more skeptical about the use of
theories of human nature, especially psychological ones. Albert rejects what he consider to be the
exaggerated assumptions of rational-choice economics, and he suggests Popper’s methodological
individualism is not the same as the one that economists often use. But he has not constructed any
systematic alternative.
The researches mentioned so far grew directly out of Popper’s non-justificationist theory of science.
Mario Bunge developed a non-justificationist theory of science, especially of physics, before he had ever
heard of Popper, and he does not view his work a part of the project known as critical rationalism. It
nevertheless can count as a version of critical rationalism: it is a non-justificationist effort to improve
standards of criticism. Bunge describes the crucial event in the later development of his philosophy as the
realization that frameworks—he calls them systems–were crucial for the growth of knowledge. Bunge’s
“systems” differ from the “frameworks,” whose usefulness is emphasized by some critical rationalists, if
they differ at all, in taking as the best critical methods and most progressive research the formal, precise
wording of theories. Bunge apparently feels more affinity with those thinkers who emphasize the use of
formal methods and who futilely seek justification, than with those who deny the possibility of
justification and deem the use of formal methods more limited than he does. This is understandable, since
he holds that the attainment of precision is crucial for rationality and, on his view precision is best
obtained with formal methods, and sometimes can be obtained only in this way. As a corollary of this
attitude, he proposes to respond to difficulties first with small changes that preserve systems, and move to
larger ones when these prove inadequate. This is the exact opposite of what Popper said, as he advocated
that one should always prefer that theory which has the highest degree of falsifiability. These thinkers,
however, do not disagree about the aim of the philosophy of science, which is to improve critical
standards so that the best possible theories are created and honed, but rather about the best means for
doing that. In the wake of Einstein, Agassi resolves this conflict by proposing that both approaches can be
used simultaneously.
In contrast to critical rationalists who emphasize the need for both theoretical frameworks and
methodological rules, there are also critical rationalists who dispense with both. Jagdish Hattiangadi,
Gunnar Andersson and David Miller are examples. Hattiangadi says that all problems are contradictions
encountered in attempts to master everyday problems of survival. Theoretical frameworks play no role in
the formulation of problems, though traditions apparently do. It is hard to see the difference. One of the
difficulties that his view encounters is that it makes it impossible to define problems well. For, the
problem posed by the assumptions {p, ~p, a, b, c} turns out to be the same as the problem posed by the
assumptions {p, ~p, x, y, z}. Another difficulty the theory faces is that it should, but does not, present a
contradiction to earlier versions of critical rationalism that it allegedly improves upon. Moreover, some
problems are due to gaps in our knowledge that are not contradictions. Formulations of good problems
thus require frameworks that include some selection rules.
Posing problems of knowledge in terms of the identification of methodological rules for gaining
knowledge was the crucial breakthrough that enabled Popper to move beyond his early Die beiden
Grundprobleme. When one dispenses with them, one has an ad hoc approach to critical methods. They
grow of themselves, Hattiangadi suggests, as attempts to solve practical problems. No other special
critical activity is needed or useful. He explains the growth of critical methods as part of the struggle for
survival: those who use the best methods to solve practical problems survive and reproduce themselves
best. This view runs the danger of relapsing into Hegelianism, since it judges as best any intellectual
development which is successful. Should fundamentalist Hinduism or Islam or Christianity (or all of them
together) win the day, will they then be the best expression of rationality?
Gunnar Andersson views Popper’s introduction of methodological rules as quite unnecessary: all
contradictions between theories and observations pose problems and all responses to them should be
43
prima facie acceptable. He takes off the table the most crucial aspect of the project of critical rationalism:
how can we best improve our critical methods and our capacity to learn from mistakes? Even without any
appeal to an evolutionary process such as that used by Hattiangadi, Andersson assumes that science will
do just fine without critical studies of its methods. He does not discuss his optimism or the fears of those
who do not share it. He says virtually nothing about non-scientific inquiry and rational action.
David Miller’s critical rationalism is the third example of attempts to characterize rationality without
explaining how the use of theoretical frameworks or methodological rules furthers it or hinders it. He
concentrates on improving criticism of the logic of justification; he ignores Popper’s crucial move from
the mere portrayal of the logic of research to the formulation of methodological rules. He agrees that
science is better off because it handles theories critically, but does not bother with the details. He ignores
the question: How is the use that science makes of criticism distinct, if at all, from other uses of it?
However, he apparently sides with Bartley’s comprehensively critical rationalism. He has effectively
bolstered Popper’s arguments against attempts to use induction to establish any degree of probability of
any theory and effectively criticized Popper’s theory of verisimilitude. Having concluded that there is no
evidence which can increase the probability that a theory is true, he concludes that there can be no good
reasons whatsoever for any theory or any course of action. All we can ask, he suggests, is: Why not? We
only have reasons for the rejection of theories, never for their endorsement.
But it does not follow from his correct observation that we can have no evidence which increases the
probability that a theory is true, that there are no good reasons to consider any theory true. Miller suggests
that in the interest of truth we should not make fanciful claims. But he says nothing about reasons for
preferring, say, highly explanatory theories over less explanatory ones, or ones that solve problems better
than others, or that we can improve our methods of elimination of theories beyond the mere random quest
for contradictions. On a commonsense understanding of good reasons, all these possibilities may
constitute good reasons for preferring some theories over others, even if they do not increase the
probability that any theory is true.
On Miller’s view it seems a person can declare true any unrefuted theory, say a minimal astrological
theory, or Descartes’ theory that souls have no extension, without violating any rationalist precept. He
does not offer any selection procedure. He relies entirely on the interest in the truth, which, he claims,
prevents arbitrariness. This is hardly enough: arbitrariness is not obvious. He rejects the possibility of
taking advantage of our ability to assign truth values as we fancy, as it is frivolous; he does not tell us
how to spot the frivolous. Talmudists and scholastics certainly have an interest in truth, are hardly
frivolous, and use arguments extensively, yet they are hardly rational in any way comparable to the
rationality of scientists. Popper’s mature philosophy began as he specified rules that should prevent
frivolity. He saw the need for methodological rules to make criticism effective.
Some critics say Miller’s version of critical rationalism seems to have lost its way. By limiting himself so
severely to logical analysis and neglecting the methodological aspects of rationality, Miller gives his
philosophy a characteristic typical of positivism; by limiting his considerations to logic, he suggests that
almost anything goes.
Theoretical frameworks are needed to direct rational thought and conduct, and methodological rules are
needed to improve criticism and to maintain critical standards. Popper took over from the psychology of
Otto Selz the idea that rational thought is directed because it is problem-oriented: without problems to
direct thought it becomes a random process. And without frameworks we cannot formulate and choose
problems well.
Miller can defend his view by explaining that he, too, recommends procedures to select theories to
consider true. This takes us back to the problems of social standards of rationality, of problem-solving, of
desiderata and of methods of critique which other critical rationalists are engaged in solving. About all
this he remains silent. Yet his view that there are no good reasons for considering some statements true
seems to render these redundant. If they are redundant, he should explain how we can do without them; if
not, he is saying what most critical rationalists agree about.
Alan Musgrave, Volker Gadenne and John Watkins all came out of Popper’s circle. But Musgrave and
Gadenne nevertheless focus on the search for some assurance that the theories they trust really are
trustworthy; Watkins wants some empirical standard to determine which theory is now the best. Their
44
peculiarity is that they seek methods of selecting credible theories or the best theories, while recognizing
the validity of the criticisms of methods of justification launched by critical rationalists.
Musgrave endorses Popper’s arguments that show the impossibility of sensible assignments to theories of
some measure of probability. But he finds wanting Popper’s way of avoiding skepticism, because Popper
fails to offer reasons for beliefs. Only if it does that can Popper respond to the charge that his view is too
skeptical. Musgrave regards his effort, then, as a vital defense of critical rationalism. In order to provide
the needed defense, he seeks a standard for reasonable belief. He says that Popper has such a solution: we
should believe that that theory which has best withstood criticism is true. He adds that Popper should
have said so more clearly.
Skepticism is the theory that no theory is any better than any other. Critical rationalism offers tentative
rules for the choice of theories to examine, not to believe in. Musgrave endorses Popper’s criticism of all
attempts to specify the probability of any theory being true. He considers his position fallibilist and
critical rationalist, because he accepts evidence to justify belief in a theory only if the evidence results
from attempts to refute it. And, he claims, no evidence justifies claims that a theory is true, but only belief
in a theory. Belief in a theory that has withstood criticism is justified, then, but not the claim that it is true.
It is not clear why Musgrave suggests that the task of justifying beliefs is less insoluble and less
superfluous than that of justifying theories.
Volker Gadenne resembles Musgrave somewhat. He agrees with Popper that theoretical science may very
well do without evidence for belief, but he disagrees with him about actions: these require decisions as to
which hypothesis is best. He suggests, then, that confirmed theories are preferable as a pragmatic ground
for belief. Unlike Musgrave, he realizes that Popper’s theory of corroboration cannot serve this purpose,
as it allots the least probable theories, the ones that take the most risks, the highest degree of
corroboration. But acting on them is still most risky. He therefore has a different theory of corroboration.
He separates content from degree of corroboration in order to justify choosing the most highly
corroborated theories to guide actions.
Admittedly we do need standards to limit the risk of the application of theories, as Agassi has pointed out.
As a matter of principle, Agassi notes, we may demand that theories be tested in severe ways in order to
reduce risk. But this procedure is not designed to increase belief or confidence in hypotheses or likelihood
of theories. (It is not clear what Gadenne claims for corroboration.) For example, two theories might be
equally applicable to some practical situation, one of which may by more risky, because it has more
consequences than its competitor. We may still prefer it as a basis for action, even though we have,
according to Gadenne’s theory, more reason to believe the weaker theory. The stronger theory may enable
us to do more. We have, for example, introduced nuclear energy even though we have far less reason, on
Gadenne’s standards for belief, to believe that using nuclear power is less risky than using coal. We use
gene-technology for various purposes, even though Gadenne’s theory of belief offers reasons to refrain
from using it. We thus have standards for application of theories in technology and other areas of life
which are quite independent of belief, thus apparently refuting Gadenne’s theory.
Gadenne might respond by contending that the belief in question is not belief in a theory but belief in the
success of its application. So, before applying it, we try to increase our belief that the application will
succeed. But this is also not the case. We seek to anticipate problems and to test, as well as we can,
whether some given application will lead to success or not. We try to apply risky theories because they
promise more. When we know we are taking considerable risks, we anticipate them as best we can, and
prepare to change course quickly. When we do not anticipate risks, but hope for great success, we simply
act to test our hopes. The realization that these always may be frustrated may lead to total paralysis on the
basis of Gadenne’s theory of the need for corroboration as a means of choice of theories that enable us to
act. Planning to solve our problems and realize our hopes employs theories with explanatory power. It
also takes into account criticism of possible courses of action, and requires decisions. Belief or
reassurance or corroboration are not required. Gadenne’s theory, just like Musgrave’s, leads us back to
numerous insoluble and superfluous problems in the search for justification: How much corroboration
must we seek before we act?
Judges must justify the sentences they impose on criminals. Proposals to take risks with the environment
or to defend it should be justified too─on a case by case basis. Social standards have to be sufficiently
agreed upon to allow for a consensus. On the core doctrine of critical rationalism, such standards cannot
45
have epistemological justification; they are based on conjectures as to how we can avoid mistakes, and
when there are different candidates, they are all subject to criticism. More cannot be done, and so all
decisions are unjustified and so they all incur risks.
John Watkins intended his theory to go beyond Popper’s suggestion that we should choose the theory that
has the highest degree of explanatory power. He wished to explain why the theory corroborated to the
highest degree is the best now available. But it is hard to see why one theory has to be identified as the
best. It is often the case that one theory will be better in one respect and another in some other respect.
Such a situation poses problems for both theories. It is reasonable to attempt to solve problems facing
each theory quite independently of which theory is now the best on available evidence—if indeed, such a
judgment can be made in any sensible way. The attempt to reduce all the good qualities to one quality
which is fundamental or the most important is quixotic, as Popper’s failed attempt to reduce all good
qualities of theory to high degree of testability illustrates. (In the development of his theory of
metaphysical research programs Agassi first pointed out that explanatory power can vary independently
from testability.) The refined theory of corroboration which Watkins offers is quite irrelevant to practice,
where what counts is adequacy for the task at hand and not some abstract measure of current success.
Also, in practice we do not want to know which theory is the best, but how various serious alternatives
may be improved. Furthermore, there is no point in trying to say which theory is the best at any given
time with such a difficult procedure as Watkins has offered: before we have determined which of two
alternatives is the best, both alternatives will very likely have been modified and we will have to start all
over again.
Theories should have good qualities before we set about criticizing them, if we are not to waste our time
in a random search. These good qualities are methodological: What does the theory explain? What
problems does it solve? How can it be criticized? They are not epistemological: What evidence do we
have for its truth? How can we be reassured we are on the right track? How do we know it corresponds to
what the truth is like? Watkins views himself as a critical rationalist even though he stresses corroboration,
because he does not relate corroboration to appraisals of the truth or probability of theories, but rather to
other good qualities of theories. But he changes the project of critical rationalism from substituting
methods of criticism for methods of justification to the quixotic project of determining which theory is
best at any given time on the basis of its corroboration.
A crucial feature of critical rationalism is the theory that social norms determine the degree of rationality
which individuals are able to exercise. This is a direct outgrowth of Popper’s use of methodological rules
to explain the growth of science. Because science is a social activity, Popper argued, Robinson Crusoe
could not do science. One individual, he suggested, cannot both put forth and criticize theories adequately.
Rationality comes from cooperation. To be effective in bringing about the growth of knowledge, criticism
should follow social rules.
This feature of critical rationalism has led to a critical rationalist sociology of science and technology.
The task of this sociology is the appraisal of the rules of science and technology. Do they encourage or
hinder the formulation and circulation of bold conjectures and their effective critical appraisal? This effort
began with Agassi’s criticisms of Popper’s rule to always prefer the theory with the highest degree of
testability: Sometimes a testable theory has a higher explanatory power than some competitor, he argued,
but also has a lower degree of testability than this competitor. We may, then, prefer it. The same holds for
Popper’s rule that all basic statements used in science should be repeatable: an independently testable
explanation of a basic statement is sufficient. From these studies he moved on to inquiries into science as
an open society. Even in the face of the traditional association of science with openness of debate and
discussion, a variety of modern thinkers such as Michael Polanyi and Thomas Kuhn have opposed this
view.
John Wettersten has continued critical rationalist studies in the sociology of science with examinations of
how adventurous and conservative styles of research complement and compete with each other, how
stylistic standards can hinder research, how a problem-oriented approach may improve standards in
science and technology, and how critical rationalism may be used to guide sociological research.
Wettersten has developed critical studies of alternative approaches to the sociology of science: a critical
rationalist approach aims at minimizing the idealization of science, but without explaining scientific
knowledge away.
46
I.C. Jarvie has recently studied how and when Popper added a theory of the institutions of science to his
theory of the logic of science (Jarvie 2001) . In The Open Society and Its Enemies Popper explicitly added
a social dimension to his view of science which was only implicit in Logik der Forschung. Popper did not,
however, move on to sociological studies of science. He was so concerned not to explain away scientific
knowledge as a mere social phenomena that he did not engage in the social studies of science even though
his view called for such studies. He did not see that the effort to minimize idealized versions of science by
describing how science encourages and hinders research poses no temptation to explain away scientific
knowledge.
As rationality is never perfect, and as idealization is to be minimized, Jarvie and Agassi tried to solve a
number of central issues in the social sciences under the assumption that rationality is a matter of degree.
This invites a new philosophical anthropology. In order to understand human nature it is desirable to
desist from seeking all-or-nothing theories of humanity as, for example, a mere machine or of rationality
as perfect. Human rationality cannot be understood apart from its mechanical or biological or social or
rational aspects; human mechanism and biology and society cannot be understood apart from their
rational aspects.
In addition to being a study of the methodology of the social sciences Popper’s The Open Society and Its
Enemies is a political manifesto. It sets minimal conditions for democratic politics: it must avoid utopian
social engineering. The exclusive use of piecemeal social engineering requires that societies be open and
that critical appraisal of government policies be carried out. Governments must set abstract conditions for
how a society functions, but they should leave individuals free to act as they choose. This freedom
includes the right of individuals to build their own social groups.
John Watkins and Bryan Magee have added significant observations about Popper’s contribution.
Watkins pointed out that Popper’s theory offered a basis for a pluralistic society which traditional theories
of rationality cannot: justificationist theories allow only one view to be justified given the evidence at any
time, whereas critical rationalism allows for a range of defensible theories which may democratically
compete in the political arena. Magee (1995) has argued that Popper’s philosophy offered a good antidote
for those who would reject existing society as no good on the basis of utopian standards and demand
radical reform. It explained why all societies have grave defects, that they could be corrected to some
degree piecemeal, but that no radical change of society had any hope of making the situation any better.
Popper’s abstract demarcation of closed and open societies does not touch most political controversies
today, which concern disagreements among defenders of the open society. As a consequence, critical
rationalists such as Jeremy Shearmur and Gerard Radnitzky have attempted to pull Popper’s theory
toward Hayek and laissez-faire economics, whereas others, such Malachi Hacohen, Agassi and Helmut
Schmidt have found in his theory a framework for theories of active social reform. Popper said very little
about competing democratic forms of government and what he has said is not necessarily connected to his
philosophical deliberations in any obvious way.
Popper’s observation that reform has unintended and unknown consequences which may then require
further adjustments or backtracking has been read as a support for Hayek’s demand that all government
should be severely limited. Popper’s observation that no society is perfect and his demand that social
reform should eliminate some of its worst aspects have been read as support of a moderate socialism.
Popper began his research as a student of the Pedagogical Institute of the University of Vienna. Members
of the Würzburg School such as Karl Bühler and Otto Selz were closely associated with the school reform
movement led by Eduard Burger. Selz explained how learning could be improved when it centred on
active problem solving. Popper adopted his view and argued that the memorization of important material
by repetition would be replaced with a Selzian, problem-orientated approach. Wettersten has explained
this as a beginning of integrated psychology and pedagogy that Popper has further developed by adding to
it his methodological insights. Other critical rationalists followed this lead stressing the import of active
problem solving, and adding the formation of conjectures and exercises in criticism and improvement of
them. Also, emphasizing Popper’s insight that science only makes advances in social settings, they have
added the demand not to ignore the fact that learning involves social interaction, whereby autonomy, as
the needed prerequisite for critical thinking, is also deemed a prime goal of any good pedagogy.
47
The salient points of critical rationalism open new possibilities in ethics, which until now has been merely
couched in terms of the need to be critical and open. A problem-oriented ethics may replace traditional
rule and consequence oriented ones. The use of critical standards of debate to appraise the history of
philosophy opens up new perspectives as illustrated in the work of Curtis on Darwin’s reception (Curtis
1987) and Wettersten’s study of the reception to Whewell. It offers new paths for the study of related
fields such as economics, where Kurt Klappholz and Lawrence Boland have led the way, for the study of
methods and historiography of psychology as mentioned, and the possibility of a new theory of
institutions as structures which individuals use to solve problems and appraise alternatives.
Various efforts such as these are still too fresh to be appraised and various defenders of critical
rationalism differ on crucial issues. Just what, if any, its long-term impact will be is still quite open;
debates among its exponents and between them and opponents are still on-going. The crucial issue is
whether and to what degree methods of criticism can be substituted for epistemological methods of
justification in all areas of life. This is the way we can face the stimulating criticism of Russell, who
viewed critical rationalism as defeatist. Only the exhibition of bold, fruitful thinking may answer it. There
is ongoing research to develop a critical theory of the history of philosophy, of the sociology of science,
of political philosophy, of ethical theory, and of social and political institutions.
48
Confirmations should count only if they are the result of risky predictions; that is to say,
if, unenlightened by the theory in question, we should have expected an event which
was incompatible with the theory - an event which would have refuted the theory. This
logical asymmetry between verification and falsification is at the heart of his philosophy
of science, and it led him to make falsifiability his criterion of demarcation between
what is and is not scientific: a theory should be considered scientific if and only if it is
falsifiable. Historicism, as Popper used the term, is the theory that history progresses by
general laws towards a determinate end Popper argued that this view underpins most
forms of authoritarianism and totalitarianism, and that it is based on mistaken
assumptions about the nature of scientific law and prediction. Moreover, they sought to
account for the presuppositions of scientific theories by regimenting such theories
within a logical framework so that the important role played by conventions, either in
the form of definitions or of other analytical framework principles, became evident.
While the Vienna Circle's early form of logical empiricism (or logical positivism or
neopositivism: these labels will be used interchangably here) no longer represents an
active research program, recent history of philosophy of science has unearthed much
previously neglected variety and depth in the doctrines of the Circle's protagonists,
some of whose positions retain relevance for contemporary analytical philosophy.
Others, like Carnap, agreed on the distinction between philosophy and science but
turned philosophy into a purely formal enterprise, the so-called logic of science. By
contrast, for Carnap, philosophy investigated, reconstructed and developed new logicolinguistic frameworks and suggested possible formal conventions for science, while, for
Neurath, philosophy was replaced by an interdisciplinary meta-theory of science that
encompassed formal as well as empirical disciplines with a pragmatic orientation.
Important topics like that of the theory and practice of unified science, of the nature of
the empirical basis of science and of the general structure of the theories of individual
sciences can only be touched upon selectively. Other matters, like the contributions
made by Vienna Circle members to the development of probability theory and inductive
logic, the philosophy of logic and mathematics (apart from the guiding ideas of Carnap)
and to the philosophy of individual empirical sciences (physics, biology, psychology,
social science), cannot be discussed at all (see Creath and Friedman forthcoming and
Richardson and Uebel forthcoming for relevant essays). Even though the formalist
project became identified with mainstream logical empiricism generally (consider its
prominence in confirmation theory and in the theory of explanation), it was not
universally subscribed to in the Vienna Circle itself.
Concerning the criticism of the circular nature of the definition of analyticity, Carnap
responded that it pertained primarily to the idea of analyticity in natural language
whereas he was interested in "explications" as provided by the logic of science (or better,
a logic of science, since there existed no unique logic of science for Carnap). Unlike the
logician of science Carnap, who left it to psychology and brain science to determine
more precisely what the class observational predicates were that could feature in
protocol statements (1936/37), the empirically oriented meta-theoretician of science
Neurath was concerned to encompass and comprehend the practical complexities of
reliance on scientific testimony (see Uebel 2005). scientific theories, Theoretical Terms
and the Problem of Realism Yet even if it be conceded that the members of the Vienna
Circle did not harbour reductionist ambitions, the question remains open whether they
were able to deal with the complexities of scientific theory building. Here the prominent
role of Schlick must be mentioned, whose General Theory of Knowledge (1918, second
49
edition 1925) was one of the first publications by (future) members of the Vienna Circle
to introduce the so-called two-languages model of scientific theories. Note that the issue
of Realism vis-à-vis Theoretical Terms is closely related to two other issues central to
the development of Vienna Circle philosophy: Carnap's further attempts to develop a
criterion of empiricist significance for the terms of the theoretical languages of science
and his attempts to defend the distinction between synthetic and analytic statements
with regard to such theoretical languages.
A term is relatively significant if and only if there exists a statement in the theoretical
language that contains it as the only non-logical term and from which, in conjunction
with another theoretical statement and the sets of theoretical postulates and
correspondence rules, an observational statement is derivable that is not derivable from
that other theoretical statement and the sets of theoretical postulates and correspondence
rules alone. Yet when Carnap offered the Ramsey method as a method of characterizing
the "empirical meaning of Theoretical Terms" it was not their empirical significance as
such but the specific empirical import of Theoretical Terms that he considered (1966,
Ch. But it would be wrong to say that "RTC → TC" specified the meaning of these
Theoretical Terms; rather, "the A-postulate states that if entities exist (referred to by the
existential quantifiers of the Ramsey sentence) that are of a kind bound together by all
the relations expressed in the theoretical postulates of the theory and that are related to
observational entities by all the relations specified by the correspondence postulates of
the theory, then the theory itself is true. What tells against Carnap's project on its own
terms is that ramseyfication trivializes the truth of physical theory in the manner
indicated: the empirical meaning of Theoretical Terms that Carnap sought to capture
simply evaporates (Demopoulos 2003). If the reconstruction of empirical theories by
ramseyfication in Carnap's fashion is unacceptable, then all explications that build on
this are called into question: explications of theoretical analyticity as much as
explications of the experiential import of theories.
So the suggestion that the criterion of empirical significance can be regarded as a
proposal for how to treat the language of science cannot be brushed aside but for the
persistent neglect of the philosophical projects of Carnap or the non-formalist left
Vienna Circle. For instance, it has been argued (Carus 1999) that Carnap correctly did
not understand Tarski's theory of truth as a traditional correspondence theory such that
truth consisted in some kind of agreement of statements or judgements and facts or the
world where the latter make true the former. Much confusion exists concerning the
Vienna Circle and history, that is, both concerning the Vienna Circle's attitude towards
the history of philosophy and science and concerning its own place in that history.
Importantly, the explications given can be of two sorts: the formal explications of the
logic of science by means of exemplary models of constructed languages, and the more
informal explications of the empirical theory of science given by spelling out how
certain theoretical desiderata can be attained more or less under practical constraints.
Non-justificationism, that is, the theory that no theory can be proven, is at least as old as
Socrates, but Popper's version of it is the first that also purports to explain the growth of
knowledge.
On a justificationist theory of the task of the philosophy of science such as
Reichenbach's, which was identical to Popper's theory as he wrote Die beiden
Grundprobleme without chapter 5, science should be demarcated by the proper
assignment of truth values: science is the set of sentences with justifiably assigned truth
50
values. On the theory presented in Die beiden Grundprobleme without chapter 5, after
science had done its job, there were still, on the one hand, some fictions which ought to
be deemed scientific such as the theories of the Würzburg school in psychology and,
perhaps, as he said later, Einstein's physics, and, on the other hand, other fictions which
should be deemed unscientific, such as the psychologies of Freud and Adler. But Popper
had at that point no non-justificationist theory of rationality in general; his theory
applied to science alone. The conflict between Popper's new theory of science and his
older theory that only proven or refuted sentences can take truth values was removed by
Tarski. Tarski did not necessarily offer Popper an adequate theory of truth for his
philosophy of science.
After his meeting with Tarski, he was free to develop his fallibilist theory of science in
new ways, because he could claim that theories could be true even though there was no
proof of them. I begin with Agassi, who developed Popper's philosophy piecemeal and
then turn to Bartley who attempted to give critical rationalism a comprehensive
statement, that is, a version of it which would explain how a critical rationalist could
adopt a critical stance toward any idea whatsoever, including its own claims. He did this
by extending Popper's theory of the methods of scientific practice to include the critical,
and thereby progressive, use of metaphysical theories to guide scientific research. For,
he argued, on the one hand, the theory of rationality as proof should itself be proven, but
in fact it is not provable, whereas, on the other hand, the theory of rationality as
readiness to appraise theories critically should itself be open to criticism, and this is
quite possible. It is then no longer the case that the adoption of a rational approach to
problems is no more rational than commitments to belief systems, such as those of some
religion: the theory that rational practice means holding all theories open to criticism,
may itself be held open to criticism.
Like many, Popper wanted the theory of science to describe science, but he hardly tried
to apply his view to the history of science. The researches mentioned so far grew
directly out of Popper's non-justificationist theory of science. Mario Bunge developed a
non-justificationist theory of science, especially of physics, before he had ever heard of
Popper, and he does not view his work a part of the project known as critical rationalism.
He has effectively bolstered Popper's arguments against attempts to use induction to
establish any degree of probability of any theory and effectively criticized Popper's
theory of verisimilitude. On Miller's view it seems a person can declare true any
unrefuted theory, say a minimal astrological theory, or Descartes' theory that souls have
no extension, without violating any rationalist precept.
Their peculiarity is that they seek methods of selecting credible theories or the best
theories, while recognizing the validity of the criticisms of methods of justification
launched by critical rationalists. Unlike Musgrave, he realizes that Popper's theory of
corroboration cannot serve this purpose, as it allots the least probable theories, the ones
that take the most risks, the highest degree of corroboration. Watkins views himself as a
critical rationalist even though he stresses corroboration, because he does not relate
corroboration to appraisals of the truth or probability of theories, but rather to other
good qualities of theories. This effort began with Agassi's criticisms of Popper's rule to
always prefer the theory with the highest degree of testability: Sometimes a testable
theory has a higher explanatory power than some competitor, he argued, but also has a
lower degree of testability than this competitor. John Wettersten has continued critical
rationalist studies in the sociology of science with examinations of how adventurous
51
and conservative styles of research complement and compete with each other, how
stylistic standards can hinder research, how a problem-oriented approach may improve
standards in science and technology, and how critical rationalism may be used to guide
sociological research.
Wettersten has developed critical studies of alternative approaches to the
sociology of science: a critical rationalist approach aims at minimizing the
idealization of science, but without explaining scientific knowledge away. I.C. Jarvie
has recently studied how and when Popper added a theory of the institutions of science
to his theory of the logic of science (Jarvie 2001) . Watkins pointed out that Popper's
theory offered a basis for a pluralistic society which traditional theories of rationality
cannot: justificationist theories allow only one view to be justified given the evidence at
any time, whereas critical rationalism allows for a range of defensible theories which
may democratically compete in the political arena. As a consequence, critical
rationalists such as Jeremy Shearmur and Gerard Radnitzky have attempted to pull
Popper's theory toward Hayek and laissez-faire economics, whereas others, such
Malachi Hacohen, Agassi and Helmut Schmidt have found in his theory a framework
for theories of active social reform. There is ongoing research to develop a critical
theory of the history of philosophy, of the sociology of science, of political philosophy,
of ethical theory, and of social and political institutions.
Keywords: 150
abstract scientific theories
adequate theory
agassi
agassi theory
all-or-nothing theories
arithmetic
axiomatized theories
bartley
bartley theory
belief
carnap
circle general theory
classical correspondence theory
confirmation theory
confirmations
conjecture
conjectures
consequence
correspondence rules
corroboration
credible theories
criterion
critical methods
critical rationalism
critical rationalist theories
critical theory
defensible theories
52
demarcation
descartes theory
desirable theories
different theory
distinction
doctrines
educational theory
empirical scientific theories
empirical theories
empirical theory
empiricism
enemies
entire theories
entire theory
ethical theory
explications
failure
fallibilism
fallibilist theory
falsification
faraday field theory
faraday theory
formalist
frameworks
gadenne theory
hermeneutic theories
high theory
history of philosophy
induction
justification
justificationist theories
justificationist theory
lakatos theory
left wing
logical empiricism
logical positivism
logical syntax
manifesto
mathematical research
mathematics
metaphysical theories
metaphysical theory
metaphysics
methodology
musgrave
neurath
neurath theory
new scientific philosophy
non-refuted theories
number theory
53
objections
of
open society
opposition
original theories
original theory
own theories
philosophers
philosophy of science
physical theory
polanyi theory
popper
popper new theory
popper non-justificationist theory
popper theory
possible theories
postulates
previous theories
principle
probability
probability theory
proof
proofs
propensity theory
psychology
quantum theory
quine
ramsey
ramseyfied theories
ramseyfied theory
rationalists
rationality
realism
reconstructed theories
reconstructions
reductionism
refined theory
refutations
refuted theories
reichenbach
relativity
research programs
risky theories
schlick
scientific knowledge
scientific method
scientific theory
scientific theory building
semantic theory
sentences
54
several competing theories
social science
superstring theory
synthetic distinction
tarski
tarski theory
testable theory
theoretical language
theoretical terms
thesis
thinkers
traditional correspondence theory
traditional theories
true unrefuted theory
truth values
underlying theory
value theory
various competing theories
verifiability
vienna circle
vienna circle theories
waismann
wittgenstein
Confirmations should count only if they are the result of risky predictions; that is to say,
if, unenlightened by the theory in question, we should have expected an event which
was incompatible with the theory - an event which would have refuted the theory. This
logical asymmetry between verification and falsification is at the heart of his philosophy
of science, and it led him to make falsifiability his criterion of demarcation between
what is and is not scientific: a theory should be considered scientific if and only if it is
falsifiable. Historicism, as Popper used the term, is the theory that history progresses by
general laws towards a determinate end Popper argued that this view underpins most
forms of authoritarianism and totalitarianism, and that it is based on mistaken
assumptions about the nature of scientific law and prediction. Moreover, they sought to
account for the presuppositions of scientific theories by regimenting such theories
within a logical framework so that the important role played by conventions, either in
the form of definitions or of other analytical framework principles, became evident.
While the Vienna Circle's early form of logical empiricism (or logical positivism or
neopositivism: these labels will be used interchangably here) no longer represents an
active research program, recent history of philosophy of science has unearthed much
previously neglected variety and depth in the doctrines of the Circle's protagonists,
some of whose positions retain relevance for contemporary analytical philosophy.
Others, like Carnap, agreed on the distinction between philosophy and science but
turned philosophy into a purely formal enterprise, the so-called logic of science. By
contrast, for Carnap, philosophy investigated, reconstructed and developed new logicolinguistic frameworks and suggested possible formal conventions for science, while, for
55
Neurath, philosophy was replaced by an interdisciplinary meta-theory of science that
encompassed formal as well as empirical disciplines with a pragmatic orientation.
Important topics like that of the theory and practice of unified science, of the nature of
the empirical basis of science and of the general structure of the theories of individual
sciences can only be touched upon selectively. Other matters, like the contributions
made by Vienna Circle members to the development of probability theory and inductive
logic, the philosophy of logic and mathematics (apart from the guiding ideas of Carnap)
and to the philosophy of individual empirical sciences (physics, biology, psychology,
social science), cannot be discussed at all (see Creath and Friedman forthcoming and
Richardson and Uebel forthcoming for relevant essays). Even though the formalist
project became identified with mainstream logical empiricism generally (consider its
prominence in confirmation theory and in the theory of explanation), it was not
universally subscribed to in the Vienna Circle itself.
Concerning the criticism of the circular nature of the definition of analyticity, Carnap
responded that it pertained primarily to the idea of analyticity in natural language
whereas he was interested in "explications" as provided by the logic of science (or better,
a logic of science, since there existed no unique logic of science for Carnap). Unlike the
logician of science Carnap, who left it to psychology and brain science to determine
more precisely what the class observational predicates were that could feature in
protocol statements (1936/37), the empirically oriented meta-theoretician of science
Neurath was concerned to encompass and comprehend the practical complexities of
reliance on scientific testimony (see Uebel 2005). scientific theories, Theoretical Terms
and the Problem of Realism Yet even if it be conceded that the members of the Vienna
Circle did not harbour reductionist ambitions, the question remains open whether they
were able to deal with the complexities of scientific theory building. Here the prominent
role of Schlick must be mentioned, whose General Theory of Knowledge (1918, second
edition 1925) was one of the first publications by (future) members of the Vienna Circle
to introduce the so-called two-languages model of scientific theories. Note that the issue
of Realism vis-à-vis Theoretical Terms is closely related to two other issues central to
the development of Vienna Circle philosophy: Carnap's further attempts to develop a
criterion of empiricist significance for the terms of the theoretical languages of science
and his attempts to defend the distinction between synthetic and analytic statements
with regard to such theoretical languages.
A term is relatively significant if and only if there exists a statement in the theoretical
language that contains it as the only non-logical term and from which, in conjunction
with another theoretical statement and the sets of theoretical postulates and
correspondence rules, an observational statement is derivable that is not derivable from
that other theoretical statement and the sets of theoretical postulates and correspondence
rules alone. Yet when Carnap offered the Ramsey method as a method of characterizing
the "empirical meaning of Theoretical Terms" it was not their empirical significance as
such but the specific empirical import of Theoretical Terms that he considered (1966,
Ch. But it would be wrong to say that "RTC → TC" specified the meaning of these
Theoretical Terms; rather, "the A-postulate states that if entities exist (referred to by the
existential quantifiers of the Ramsey sentence) that are of a kind bound together by all
the relations expressed in the theoretical postulates of the theory and that are related to
observational entities by all the relations specified by the correspondence postulates of
the theory, then the theory itself is true. What tells against Carnap's project on its own
terms is that ramseyfication trivializes the truth of physical theory in the manner
56
indicated: the empirical meaning of Theoretical Terms that Carnap sought to capture
simply evaporates (Demopoulos 2003). If the reconstruction of empirical theories by
ramseyfication in Carnap's fashion is unacceptable, then all explications that build on
this are called into question: explications of theoretical analyticity as much as
explications of the experiential import of theories.
So the suggestion that the criterion of empirical significance can be regarded as a
proposal for how to treat the language of science cannot be brushed aside but for the
persistent neglect of the philosophical projects of Carnap or the non-formalist left
Vienna Circle. For instance, it has been argued (Carus 1999) that Carnap correctly did
not understand Tarski's theory of truth as a traditional correspondence theory such that
truth consisted in some kind of agreement of statements or judgements and facts or the
world where the latter make true the former. Much confusion exists concerning the
Vienna Circle and history, that is, both concerning the Vienna Circle's attitude towards
the history of philosophy and science and concerning its own place in that history.
Importantly, the explications given can be of two sorts: the formal explications of the
logic of science by means of exemplary models of constructed languages, and the more
informal explications of the empirical theory of science given by spelling out how
certain theoretical desiderata can be attained more or less under practical constraints.
Non-justificationism, that is, the theory that no theory can be proven, is at least as old as
Socrates, but Popper's version of it is the first that also purports to explain the growth of
knowledge.
On a justificationist theory of the task of the philosophy of science such as
Reichenbach's, which was identical to Popper's theory as he wrote Die beiden
Grundprobleme without chapter 5, science should be demarcated by the proper
assignment of truth values: science is the set of sentences with justifiably assigned truth
values. On the theory presented in Die beiden Grundprobleme without chapter 5, after
science had done its job, there were still, on the one hand, some fictions which ought to
be deemed scientific such as the theories of the Würzburg school in psychology and,
perhaps, as he said later, Einstein's physics, and, on the other hand, other fictions which
should be deemed unscientific, such as the psychologies of Freud and Adler. But Popper
had at that point no non-justificationist theory of rationality in general; his theory
applied to science alone. The conflict between Popper's new theory of science and his
older theory that only proven or refuted sentences can take truth values was removed by
Tarski. Tarski did not necessarily offer Popper an adequate theory of truth for his
philosophy of science.
After his meeting with Tarski, he was free to develop his fallibilist theory of science in
new ways, because he could claim that theories could be true even though there was no
proof of them. I begin with Agassi, who developed Popper's philosophy piecemeal and
then turn to Bartley who attempted to give critical rationalism a comprehensive
statement, that is, a version of it which would explain how a critical rationalist could
adopt a critical stance toward any idea whatsoever, including its own claims. He did this
by extending Popper's theory of the methods of scientific practice to include the critical,
and thereby progressive, use of metaphysical theories to guide scientific research. For,
he argued, on the one hand, the theory of rationality as proof should itself be proven, but
in fact it is not provable, whereas, on the other hand, the theory of rationality as
readiness to appraise theories critically should itself be open to criticism, and this is
quite possible. It is then no longer the case that the adoption of a rational approach to
57
problems is no more rational than commitments to belief systems, such as those of some
religion: the theory that rational practice means holding all theories open to criticism,
may itself be held open to criticism.
Like many, Popper wanted the theory of science to describe science, but he hardly tried
to apply his view to the history of science. The researches mentioned so far grew
directly out of Popper's non-justificationist theory of science. Mario Bunge developed a
non-justificationist theory of science, especially of physics, before he had ever heard of
Popper, and he does not view his work a part of the project known as critical rationalism.
He has effectively bolstered Popper's arguments against attempts to use induction to
establish any degree of probability of any theory and effectively criticized Popper's
theory of verisimilitude. On Miller's view it seems a person can declare true any
unrefuted theory, say a minimal astrological theory, or Descartes' theory that souls have
no extension, without violating any rationalist precept.
Their peculiarity is that they seek methods of selecting credible theories or the best
theories, while recognizing the validity of the criticisms of methods of justification
launched by critical rationalists. Unlike Musgrave, he realizes that Popper's theory of
corroboration cannot serve this purpose, as it allots the least probable theories, the ones
that take the most risks, the highest degree of corroboration. Watkins views himself as a
critical rationalist even though he stresses corroboration, because he does not relate
corroboration to appraisals of the truth or probability of theories, but rather to other
good qualities of theories. This effort began with Agassi's criticisms of Popper's rule to
always prefer the theory with the highest degree of testability: Sometimes a testable
theory has a higher explanatory power than some competitor, he argued, but also has a
lower degree of testability than this competitor. John Wettersten has continued critical
rationalist studies in the sociology of science with examinations of how adventurous
and conservative styles of research complement and compete with each other, how
stylistic standards can hinder research, how a problem-oriented approach may improve
standards in science and technology, and how critical rationalism may be used to guide
sociological research.
Wettersten has developed critical studies of alternative approaches to the sociology of
science: a critical rationalist approach aims at minimizing the idealization of science,
but without explaining scientific knowledge away. I.C. Jarvie has recently studied how
and when Popper added a theory of the institutions of science to his theory of the logic
of science (Jarvie 2001) . Watkins pointed out that Popper's theory offered a basis for a
pluralistic society which traditional theories of rationality cannot: justificationist
theories allow only one view to be justified given the evidence at any time, whereas
critical rationalism allows for a range of defensible theories which may democratically
compete in the political arena. As a consequence, critical rationalists such as Jeremy
Shearmur and Gerard Radnitzky have attempted to pull Popper's theory toward Hayek
and laissez-faire economics, whereas others, such Malachi Hacohen, Agassi and Helmut
Schmidt have found in his theory a framework for theories of active social reform.
There is ongoing research to develop a critical theory of the history of philosophy, of
the sociology of science, of political philosophy, of ethical theory, and of social and
political institutions.
Keywords: 150
abstract scientific theories
58
adequate theory
agassi
agassi theory
all-or-nothing theories
arithmetic
axiomatized theories
bartley
bartley theory
belief
carnap
circle general theory
classical correspondence theory
confirmation theory
confirmations
conjecture
conjectures
consequence
correspondence rules
corroboration
credible theories
criterion
critical methods
critical rationalism
critical rationalist theories
critical theory
defensible theories
demarcation
descartes theory
desirable theories
different theory
distinction
doctrines
educational theory
empirical scientific theories
empirical theories
empirical theory
empiricism
enemies
entire theories
entire theory
ethical theory
explications
failure
fallibilism
fallibilist theory
falsification
faraday field theory
faraday theory
formalist
frameworks
59
gadenne theory
hermeneutic theories
high theory
history of philosophy
induction
justification
justificationist theories
justificationist theory
lakatos theory
left wing
logical empiricism
logical positivism
logical syntax
manifesto
mathematical research
mathematics
metaphysical theories
metaphysical theory
metaphysics
methodology
musgrave
neurath
neurath theory
new scientific philosophy
non-refuted theories
number theory
objections
of
open society
opposition
original theories
original theory
own theories
philosophers
philosophy of science
physical theory
polanyi theory
popper
popper new theory
popper non-justificationist theory
popper theory
possible theories
postulates
previous theories
principle
probability
probability theory
proof
proofs
propensity theory
60
psychology
quantum theory
quine
ramsey
ramseyfied theories
ramseyfied theory
rationalists
rationality
realism
reconstructed theories
reconstructions
reductionism
refined theory
refutations
refuted theories
reichenbach
relativity
research programs
risky theories
schlick
scientific knowledge
scientific method
scientific theory
scientific theory building
semantic theory
sentences
several competing theories
social science
superstring theory
synthetic distinction
tarski
tarski theory
testable theory
theoretical language
theoretical terms
thesis
thinkers
traditional correspondence theory
traditional theories
true unrefuted theory
truth values
underlying theory
value theory
various competing theories
verifiability
vienna circle
vienna circle theories
waismann
wittgenstein
61
Search: 0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ
Coverage: 50%
1
1930s 322, 394
1932 onwards 1080
1958 onwards 972
2
2 january 1930 513
A
a.j. ayer 331
abel rey 1195
absence 1559
ad hoc
ad hoc auxiliary 14
ad hoc maneuver 1510
ad hoc protection 1513
afterlife 115
agassi
agassi 2045, 1724, 1756, 1785, 1999, 1396, 1581, 1676, 1681
agassi theory 1724, 1756, 1785, 1999
joseph agassi 1396
ake petzall 331
albert
albert blumberg 331
albert einstein 140
ambitions 806, 861, 1242
american professors 97, 1344
and gower 1198
approach work 1112
aristotle 51
arithmetic 406, 730, 746, 736, 28
arne naess 331
assertion 37
assumption
assumption 14
atom smasher 68
B
back door 43
62
bartley
bartley 1785, 1652, 1784
bartley theory 1785, 1652
basic particles 83, 105
beiden grundprobleme
beiden grundprobleme 1480, 1446
beiden grundprobleme der erkenntnistheorie 1446
die beiden grundprobleme der erkenntnistheorie 1446
belief
belief 1626, 1627, 1923, 1926, 1928, 1949, 1932, 1938, 1948, 254, 1931, 111
belief confidence 1938
belief systems 1626, 1627
bergmann 1987 332
berlin
berlin group 1276
berlin society 360
betoken foundationalism 815
black crow
black crows 37
crows 37, 63
white crow 62
blunder 57
boltzmann 316
book
book series zur wissenschaftlichen weltauffassung 370
books tools theories models libraries computers networks 26
brentano school 1195
bunge 1814
C
cardinality constraint
cardinality constraint 1024
carnap
1935 carnap 342, 343
carnap 852, 1145, 316, 360, 987, 997, 1043, 332, 358, 976, 1001, 1025, 1052, 1268,
1109, 377, 525, 556, 560, 625, 646, 663, 747, 759, 767, 768, 806, 855, 859, 900, 911,
939, 1160, 1181, 96, 116, 120, 262, 322, 353, 364, 406, 508, 553, 555, 557, 568, 576,
583, 591, 676, 687, 689, 701, 706, 711, 714, 716, 718, 721, 724, 726, 730, 733, 742,
746, 753, 769, 774, 789, 796, 831, 834, 837, 846, 858, 861, 862, 931, 933, 938, 940,
946, 947, 959, 965, 971, 982, 983, 998, 1035, 1049, 1066, 1074, 1080, 1091, 1092,
1094, 1101, 1112, 1113, 1165, 1175, 1180, 1205, 1269, 1343, 1365, 1369, 92, 118, 119,
123, 318, 342, 343, 526, 541, 542, 546, 552, 601, 680, 681, 693, 696, 699, 709, 715,
722, 736, 740, 761, 771, 781, 783, 788, 791, 794, 805, 836, 841, 886, 887, 908, 920,
925, 932, 934, 935, 942, 950, 957, 963, 972, 999, 1000, 1002, 1013, 1014, 1015, 1018,
1031, 1032, 1033, 1047, 1051, 1055, 1060, 1069, 1088, 1089, 1090, 1134, 1135, 1182,
1187, 1188, 1189, 1198, 1206, 1251, 1339, 1367, 1368, 1372
carnap 1934/37 1060
carnap 1936-37 526
carnap 1936-37 37n 526
63
carnap 1942 preface 724
carnap 1963 332
carnap neurath 316, 360, 332, 358, 1268, 377, 525, 625, 855, 859, 353, 1165
carnap quine 911, 718, 1066
carnap reichenbach 364
carnap schlick 316, 360, 358, 1268, 525, 1205, 458, 778
editor-in-chief carnap 377
post-aufbau carnap 862
rudolf carnap 316, 262, 92, 1339
carnap hahn
carnap hahn frank neurath 316, 525, 625
carnap hahn neurath 316, 360, 332, 358, 525, 625
cartesian dualism 188
charles
charles morris 377, 331
charles peirce 100, 101, 142
circle
circle members 490, 879, 378, 1207, 333, 339, 424, 813
circle position 862, 386, 393, 427, 445, 492, 1213
circle schlick 360, 358, 1268, 378, 1207, 865
cognition 20, 23
compelling evidence 76
complexities 874, 851
concept
useless concept 92, 1339
conception
scientific world conception 360, 358, 370
world conception 360, 358, 370
conceptual systems 681
confirmation
confirmation theory 1
confirmations 1, 2, 50, 63, 89
conjecture
conjecture 34, 92, 188, 1281, 1339, 38, 49, 54, 56, 59, 60, 65, 66, 69, 77, 79
conjectures 34, 264, 1281
conjectures refutations 264
consequence
consequence 1043, 1041, 968
observational consequences 1044
constructivist
constructivists postmodernists 97, 1344
social constructivists 97, 1344
contact
contacts visitors 312
international contacts 312
contradictions 1873
correspondence
correspondence postulates 991
correspondence rules 846
64
correspondence truth 1145, 1168, 163, 1148
correspondences likenesses 1151
correspondence theory
correspondence theory 1145, 1168, 991, 1151
traditional correspondence theory 1145
corroboration 1933, 1953, 93, 1340, 1934, 1979, 1988, 1935, 1985, 40, 41, 42, 45
cosmological constant 53
cosmological model 51
criterion
1956 criterion 959, 1074, 1101, 1112, 783, 968
criterion 517, 1109, 556, 939, 508, 555, 557, 576, 591, 940, 959, 1074, 1094, 1101,
1112, 1113, 492, 495, 552, 616, 617, 618, 621, 782, 783, 950, 968, 135
meaning criterion 517, 555, 552, 621
critical appraisal 1396
critical methods 1591, 1819
critical rationalism 1785, 1775, 1798, 1990, 1801, 1917, 2035, 1995
critical standards 1827
D
december
22 december 1929 513
december 1930 513
deductive system 263
degree
one degree 1933, 1825
demarcation
demarcation 517, 591, 201, 1468, 135
demarcation criterion 517, 591, 135
disconfirmation 72
discovery
discovery justification 1175
discussion
discussion circle 663, 394
disposition
disposition statements 556
disposition terms 971
self-regulation cognition consciousness dispositions 23
dissertation 1556
distant suns 76
distinction
distinction 239, 759, 911, 742, 753, 769, 938, 1175, 448, 655, 666, 713, 771, 782,
808, 968, 999, 1254
distinction (1938) 1175
distinctions 1074, 1092, 1175
echoed distinctions 1175
synthetic distinction 769, 938, 655, 666, 771, 782, 968, 999, 1254
doctrine
doctrines 278, 322, 808
65
dogma
dogmas 249, 714, 655
two dogmas 714, 655
E
economist friedrich hayek 207
edition
editions (1946) 568
egotism 116, 1365
eino kaila 331
elaboration 393
empirical theory
empirical adequacy 896, 1035
empirical theories 1043, 1052, 890, 1587, 896, 1596
empirical theory 1267, 1266
empiricism
empiricism 396, 270, 276, 347, 655, 808, 1172, 1243
logical empiricism 276, 347, 808, 1172
viennese empiricism 808
empiricist
empiricist criterion 939, 1094
enemy
enemies 1414, 108
enemies (1945) 108
enlightenment
enlightenment 333
enlightenment reason 333
enormous impact 1603
entire theory
entire theories 976, 578
entire theory 1486, 984
entities 1025
ernest nagel 331, 91
ernst cassirer 463
erudition 110
euclidean geometry 418
existence claims 1013
experiences 20
experiential support 508
explication
behaviourist explications 852
explication 796, 1094, 693
explications 852, 1267, 1266, 1160
explicationist project 1000
extensionalist agenda 716
F
66
faction 1207, 872
factual content 984
failure 1034, 1533, 646
fallibilism 687, 100, 142
falsification 238, 240, 557, 137, 35, 37, 61, 65, 66, 90
faraday
faraday field theory 1764
faraday theory 1603, 1764
feigl
feigl 332, 322, 319, 813
feigl 1943 332
feigl 1969a 1969b 332
feigl carnap 332, 322
feigl waismann 319
herbert feigl 319
fictions 1482
field
field theory 1600, 1764, 2066
higgs field 67, 70, 79
fifth congress 360
first conference 360
flexibility 742
form content status 865
formal conventions 455
formalist
formalist project 1000
formation tranformation 1064
free wills 112
frege russell
bertrand russell 31, 1278
frege russell 1276, 676
frege russell wittgenstein 1276, 676
freud adler 1482
G
general theory
general relativity 1236
general theory 877, 879, 1519, 1567, 194, 212, 878, 1538
gerard radnitzky 2044
german neo-kantianism 1205, 1195
giorello 1981 1718
grunberg 1995 1187
gustav bergmann 316
H
h.a. lindemann 331
67
han
hans albert 1775
hans georg gadamer 1801
hans-otto apel 1801
hasso härlen 331
helmut schmidt 2045
hempel
carl gustav hempel 331
hempel (1958) 931
hempel 1935 778
henri poincaré 1195
historicism
historicism 194, 111
historiography 2066, 1676
history
history of philosophy 1181, 99
history of science 1181
human rationality 2024
hypothesis
hypotheses 1556, 1938, 254
hypotheses likelihood 1938
hypotheses observations 254
I
icy slopes 1180
impossibility 1907
impressive work 107
imre lakatos 240, 205
induction
induction 1867, 34, 125, 1281, 1383, 44, 45, 46, 71, 73, 85, 87
induction procedures 87
inductive inference
inductive inference 1467
inductive inferences 1443
infinite sequence 730
instances 474, 34, 1281, 47, 126
intense jealousy 116, 262, 1365
interested scientists 307
international encyclopedia 377, 859, 1185
investigations 911
J
jeremy shearmur 2044
john
john watkins 1966, 1652, 1902
john wettersten 2011
68
judgement
judgement 900, 591
reserve judgement 591
justification
justification 1537, 1538, 1957
justificationist theory
justificationist theories 1483, 2034, 2036
justificationist theory 1810, 1427, 1519, 1814, 1533
jørgen jørgensen 331
K
karl
karl popper 1427, 371, 31, 323, 1278, 1363, 1446, 30
karl raimund popper 1363
knowledge
knowledge claims 420
scientific knowledge 396, 1427, 1537, 264, 2012, 148
koetsier
koetsier p. 170-171 1756
kurt
kurt reidemeister 321
L
language
constructed languages 1267, 1101, 1113
deep-sounding language 1116
formal languages 1267, 585, 693
language carnap 911, 568, 576, 846, 983, 1091, 1092, 1101, 118, 1088, 1089, 1090,
1367
language constructions 831, 837
language constructor 1091, 1092, 1088, 1089, 1090
language forms 911, 1080
language truth logic 568, 1213
observational language 982
two languages 1267, 890
left wing 525, 1207, 1269, 872
logic
logic mathematics 490
math logic 490, 98
one logic 676
logical syntax
logical relation 92, 1339
logical syntax 701, 711, 726, 733
logician
logician 316
logik d
logik der 1486, 2015
69
logik d forschung
logik der forschung 1486, 2015
london school 207
ludovico geymonat 331
M
magee (1995) 2038
malachi hacohen 2045
manifesto
manifesto 1414, 328
political manifesto 1414
marburg variety 1195
marcel natkin 319
mario bunge 1814
marxism 138
mathematician
german physicists mathematicians 360
mathematician 316, 321
mathematicians 316, 360
mathematics 490, 1739, 1750
meaning determination 447
member
former members 346
member associate
associates protegées 333
member associate 323
menger
menger 321
menger kraft 321
metaphysical field
metaphysical field 1600
metaphysical field theory 1600
metaphysical theory
metaphysical theories 1591, 1396, 1559, 1561, 1556
metaphysical theory 1591, 1756, 1600
metaphysics 517, 1592, 420, 492, 1594
methodology
methodology 1545, 212, 1549
methods historiography 2066
mid-september 1929 360
monograph
monographs 386
musgrave
alan musgrave 1902
musgrave 1907, 1919, 1957, 1958, 1904, 1929, 1902
musgrave gadenne 1957, 1958, 1904, 1902
N
70
necessity
necessity (1947) 715
need standards 1936
negation 508
neglect 1109
neurath
neurath 852, 316, 360, 332, 358, 1268, 377, 525, 625, 855, 859, 1160, 353, 796, 834,
1165, 369, 386, 451, 612, 621, 851, 857, 1148, 1185
neurath 1929-and 332
neurath 1932a 458, 778
neurath 1936 332
neurath carnap 316, 360, 332, 358, 1268, 377, 525, 625, 855, 859, 353, 1165
neurath theory 852
neurath frank
frank (1932) 386
frank 1941 332
frank 1941 1949a 332
frank 1949a 332
frank hahn neurath 316, 525, 625, 1148
hahn frank neurath 316, 525, 625, 1148
neurath frank 316, 332, 525, 625, 1160, 796, 386, 612, 621, 1148
neurath frank hahn 316, 525, 625, 1148
philipp frank 316
new solution 583
newman
newman 1928 1025
newton 1764
niels bohr 141
notions 1151, 706, 1091
O
objections 163
objective knowledge
objective knowledge 264, 158
objective knowledge (1972) 264
observation
observation statements 549, 782
observation terms 560, 931, 782
old chair 316
one component 987, 655
one counterexample 133
one hand 1482, 769
one issue 1221, 1236
one quality 1975
one respect 1970
one way 290
open society
open societies 109
71
open society 1414, 108
the open society 1414, 108
opposition 492, 526
original theory
original theories 1021
original theory 978
otto
otto neurath 316
P
paper (1938) 1177
paralysis 1953
paris address
paris address 555
paris addresses 555
parts company 1806
paul feyerabend 205
peculiarity 1906
pedagogical institute 2051
periphery 312
personal perceptions 20
philosopher
american philosopher 100, 101
philosopher charles peirce 100, 101
philosopher historian 321
philosophers 125, 188, 205, 270, 307, 312, 495, 605, 1379, 1383, 1520
scientifically philosophers 307
scientists philosophers 307
two philosophers 205, 312
way philosophers 125, 1383
philosophical projects 1109
philosophy
empirical philosophy 1276
philosophies 467, 1236
philosophy history 1181, 278, 1241, 279, 99
philosophy politics economics 210
philosophy science
philosophy of science 316, 1181, 1172
philosophy science 1528, 316, 1181, 1276, 278, 447, 1241, 137, 204, 205, 253, 279,
347, 448, 1172, 1190, 1221, 1272, 1425, 1472, 1488, 1494, 1555, 1827
physical theory
physical theories 1591, 1396, 1559, 1561, 1556, 1602
physical theory 1591, 682, 1048, 1756, 1044, 1600, 1649
physical universe 18, 114
physicalism 852, 805, 841
physicists 360, 70, 79
pierre duhem 1195
popper
credit popper 99
72
forschung popper 1537
popper 1591, 1933, 2037, 1528, 1486, 1524, 1679, 1810, 2014, 103, 160, 165, 239,
1350, 1417, 1427, 1460, 1519, 1527, 1537, 1567, 1718, 1719, 1739, 1866, 1867, 1966,
1975, 1999, 2044, 1414, 1784, 1806, 1907, 96, 116, 120, 240, 262, 371, 1343, 1365,
1369, 1408, 31, 97, 188, 201, 204, 207, 210, 226, 253, 254, 264, 323, 1278, 1344, 1363,
1446, 1468, 1549, 1581, 1676, 1677, 1681, 1902, 1931, 2015, 2016, 2038, 2051, 29, 30,
32, 33, 43, 44, 45, 66, 74, 75, 90, 99, 106, 107, 108, 110, 113, 117, 124, 138, 142, 146,
147, 157
popper and/or lakatos 1739
popper new theory 1524
popper non-justificationist theory 1810
popper theory 1591, 1933, 2037, 1528, 1524, 1810, 1417, 1527, 1718, 1719, 1866,
1867, 1966, 1975, 1999, 2044
popper bartley
popper bartley 1784
position
1956 position 959, 1055
positivism
logical positivism 808, 122
positivism 808, 122
possibilities 768, 1876
postulate
meaning postulates 701
postulates 984, 989, 991, 701
postulates correspondence 991
pragmatic approach 625, 1112
pragmatic orientation 456
pragmatist
pragmatist tradition 1195
pragmatists 1276, 1195
precise wording 1819
presuppositions 273
prima facie 865
principle
principle 516
priori
a priori framework 1064, 1063
probability
probabilities 175, 105
probability 490, 103, 1350, 1867, 1868, 1871, 1875, 1907, 1919, 1985, 40, 104
probability theory 490, 103, 1350, 1867, 1868, 1871, 1875, 1919
subjective probabilities 175
problem
problem situation 150
prohibition 5
proof
proof 1624, 1689, 1534, 28
proposal
1956 proposal 968, 1251
proposal 1043, 1109, 846, 983, 1094, 957, 968, 1251
73
proposals 585, 591, 1080
two proposals here-can 591
protagonists 278, 447
psychoanalysis marxism 138
psychology
psychology 1482, 2066
publication
publication activity 377
publication project 859
Q
quantitative basis 175
quantum
quantum field 67
quantum mechanics 86, 139
quine
ones quine 911
quine 747, 759, 911, 687, 714, 716, 718, 721, 746, 753, 998, 1066, 331, 655
quine quinean 718
w.v.o. quine 331
R
ramsey
ramsey 1043, 984, 933, 965, 1002, 1015
ramsey method 933, 965, 1002, 1015
ramsey sentence
ramsey sentence 1043, 984
ramsey sentences 1043
ramseyfication concern 935
rationalist
rationalist approach 2012
rationalist sociology 1408, 1995, 2011
rationalist studies 2011
rationalists 2044
rationality 2037, 1519, 1545, 1785, 1791, 1396, 1521, 1538, 1624, 1990, 1432, 2024
realism
realism 161, 875, 813, 934, 1015
realism anti-realism 934
realist
realist 140
realist approach 140
realization 1953
reconstruction
reconstruction 1052, 890, 1021, 736
reconstructions 1043, 1001, 1160, 831
reconstructions explications 1160
74
reduction
reduction chains 560
reductionism
reductionism 808, 826
refutation
refutations 264
refutations (1963) 264
reichenbach
reichenbach 1276, 364, 1175, 328
reichenbach (1938) 1175
reichenbach grelling dubislav 328
reisch
reisch 1991 1187
relativity 416, 417, 418, 1236
relevance 1268
reorientation 663
repulsive force 54
research
mathematical research 1718, 1719, 1724, 1750, 1734
metaphysical research 1591, 1756, 1596
progressive research 1591, 1819
research traditions 1734
research program
research program 1718, 1719, 1724, 1756, 1785, 1596, 240, 276
research programs 1718, 1719, 1724, 1756, 1785, 1596, 240
two research programs 1596
researchers students 331
revisionist scholarship-consisting 1270
rey duhem 890, 1195
roger penrose 70
rules methods 1409
rutte 1986 489
S
sarkar
sarkar 2004 1198
schlick
schlick 316, 360, 1168, 358, 1268, 885, 889, 378, 525, 1207, 370, 371, 447, 865,
1205, 319, 339, 458, 513, 529, 612, 613, 615, 616, 617, 618, 666, 674, 778, 866, 872,
1177
schlick (1931) 529
schlick (1934) 865, 666
schlick 1930 458, 513
schlick 1935a 778
schlick carnap neurath 316, 360, 358, 1268, 525, 458, 778
schlick circle 360, 358, 1268, 378, 1207, 865
schlick frank 316, 525, 370, 371, 612
schlick neurath 316, 360, 358, 1268, 525, 458, 612, 778
schlick waismann 319, 513
75
science
exact sciences 360
formal sciences 396, 270, 872
human sciences 424
inductive sciences 316
mere science 1561, 463, 713
modern science 97, 1243, 1344
physical sciences 270
science carnap 316, 377, 855, 859, 789, 858, 861
science edgar zilsel 321
science methodology 1545, 1549
science neurath 316, 377, 855, 859, 451, 851, 857, 1185
science non-science 201, 1468
science philosophy 1528, 316, 1181, 1276, 278, 447, 1241, 137, 204, 205, 253, 279,
347, 448, 1172, 1190, 1221, 1272, 1425, 1472, 1488, 1494, 1555, 1827
science technology 1995
theoretical science 560, 939, 782, 1124, 1254, 1931
unified science 377, 369, 427, 451
scientific discovery
scientific discovery 226, 254, 264, 157
scientific discovery popper 264
scientific method 890, 154, 36
scientific theory
abstract scientific theories 577
empirical scientific theories 1043, 890, 896
scientific theories 1591, 877, 1043, 875, 885, 889, 890, 1064, 1234, 1396, 1482,
1559, 131, 140, 154, 273, 577, 883, 896, 1063, 1556, 1592
scientific theory 1591, 997, 396, 984, 1427, 1537, 1567, 1718, 1719, 5, 15, 132, 134,
151, 874, 930
scientific theory building 874
sentence
sentences 1043, 1524, 1447, 1467, 1470
series einheitswissenschaft 369
social science
social dimension 2015
social science 1791, 1181, 97, 1344, 2015
social sciences 316
social scientist 316
society
democratic societies 109
sociological studies 2016
statement
evidence statements 865, 549
expression statement 774
protocol statements 852
singular statements 529
statement fact 753, 774
steering mechanisms 1405
stratagem
stratagem 17
76
student imre lakatos 240
suggestion 1966, 1109
sum total 25
synthetic content 1043, 984
T
taking account 290
tarski
tarski 1145, 1528, 1524, 1529, 160, 1527, 1531, 721, 724, 998
tarski quine 998
tarski theory 1145, 160, 1531
tensile strength 83
term
descriptive terms 553, 681
theoretical terms 1048, 875, 930, 977, 996, 560, 883, 939, 846, 931, 933, 940, 946,
965, 1074, 782, 937, 963, 968, 1013, 1051
testability 1975, 1999, 557, 11
theoretical language
theoretical language 846, 983, 968
theoretical language carnap 846, 983
theory
adequate theory 1528, 1798
all-or-nothing theories 2024
atomic theory 1764
axiomatized theories 585
credible theories 1906
critical rationalist theories 1646
critical theory 1591, 1622, 1623, 1785, 1775, 1798
defensible theories 2035
descartes theory 1878
desirable theories 1592
different theory 1486, 1934
disconnected theory 263
educational theory 1417
fallibilist theory 1529, 1535
false theory 1529, 1451
gadenne theory 1953, 1943, 1947, 1957, 1958
hermeneutic theories 1801
high theory 1933, 1966, 1975, 1999, 977, 1825
lakatos theory 1718, 1719, 1750, 1723, 1731
left-leaning political theories 1414
mathematical theories 1025, 1734
non-refuted theories 1493
number theory 728
one theory 1933, 987, 997, 175, 1507, 1825, 1969, 1970, 2066
own theories 776
polanyi theory 24
political theory 1775
possible theories 1826
77
premises theories 1443
previous theories 1732
propensity theory 103, 1350
reconstructed theories 1025
refined theory 1979
refuted theories 1493, 1498
relevant theories 221
risky theories 1952
superstring theory 88, 1335
tentative theories 156, 1917
testable theory 1998
theories and/or methods 1751
theory building 874
theory choice 1953, 474
theory of knowledge 1689
theory practice 1591
traditional theories 2037
true unrefuted theory 1877
two theories 877, 890, 26, 1483, 1904, 1941
underlying theory 517
value theory 1524, 489
various competing theories 1432
thesis
theses 1080, 393, 394
thesis 746, 513, 709
thin air 54
thinkers 1827, 101
thought
rational thought 1405
three world
chapters three four 226
three world conjecture 188
three worlds 114
world three 188, 114
time
time carnap 119, 934, 1368
totalitarian regimes 109
touchstone 1236
truth
truth (1963) 759
truth conditions 1035
truth probability 1985
truth value
truth value 1524, 1497, 1498, 1467, 1470
truth values 1524, 1497, 1498, 1467, 1470
tscha hung 331
twenty years 834
two issues 937
two sets 1483
two sorts 1267
78
two ways 64
U
utopian standards 2038
V
vantage point 1276
variety depth 278
verifiability 625
verification
verification falsification 557, 137
verifications 1
verificationism 625, 526
verisimilitude 1866
vienna
university of vienna 316
vienna one 333, 655
vienna circle
neo-kantian cassirer-the vienna circle 1276
vienna circle 360, 490, 879, 358, 1268, 1109, 378, 646, 663, 767, 806, 900, 1207,
1276, 862, 270, 276, 290, 305, 307, 333, 346, 424, 434, 445, 467, 477, 605, 645, 655,
808, 813, 815, 826, 901, 936, 937, 1124, 1163, 1200, 1213, 1219, 1242, 1247, 1270,
1379
vienna circle anti-foundationalism 862
vienna circle development 490, 1268, 937
vienna circle doctrines 808
vienna circle members 490, 879, 378, 1207, 333, 424, 813
vienna circle philosophers 605
vienna circle positions 445
vienna circle philosophy
vienna circle philosophies 467
vienna circle philosophy 490, 1268, 646, 290, 333, 445, 477, 645, 826, 936, 937,
1163, 1219, 1242, 1247, 1270
vienna circle philosophy itself-seems 645
viennese academia 333
view
one view 2036
virtue 8
volker
volker 1902
volker gadenne 1902
W
waismann
friedrich waismann 319
waismann 319, 393, 394, 513
79
war ii
war ii development 347
war ii network 312
water on mars 49
wittgenstein
russell wittgenstein 1276, 676, 711
wittgenstein 1276, 676, 711, 513, 516, 1200
world war
world 2 activities 27
world one 901
world war 312, 347
world war ii 312, 347
würzburg school 1482
80
SUMMARY
Confirmations should count only if they are the result of risky predictions; that is to say,
if, unenlightened by the theory in question, we should have expected an event which
was incompatible with the theory - an event which would have refuted the theory. This
logical asymmetry between verification and falsification is at the heart of his philosophy
of science, and it led him to make falsifiability his criterion of demarcation between
what is and is not scientific: a theory should be considered scientific if and only if it is
falsifiable. Historicism, as Popper used the term, is the theory that history progresses by
general laws towards a determinate end Popper argued that this view underpins most
forms of authoritarianism and totalitarianism, and that it is based on mistaken
assumptions about the nature of scientific law and prediction. Moreover, they sought to
account for the presuppositions of scientific theories by regimenting such theories
within a logical framework so that the important role played by conventions, either in
the form of definitions or of other analytical framework principles, became evident.
While the Vienna Circle's early form of logical empiricism (or logical positivism or
neopositivism: these labels will be used interchangably here) no longer represents an
active research program, recent history of philosophy of science has unearthed much
previously neglected variety and depth in the doctrines of the Circle's protagonists,
some of whose positions retain relevance for contemporary analytical philosophy.
Others, like Carnap, agreed on the distinction between philosophy and science but
turned philosophy into a purely formal enterprise, the so-called logic of science. By
contrast, for Carnap, philosophy investigated, reconstructed and developed new logicolinguistic frameworks and suggested possible formal conventions for science, while, for
Neurath, philosophy was replaced by an interdisciplinary meta-theory of science that
encompassed formal as well as empirical disciplines with a pragmatic orientation.
Important topics like that of the theory and practice of unified science, of the nature of
the empirical basis of science and of the general structure of the theories of individual
sciences can only be touched upon selectively. Other matters, like the contributions
made by Vienna Circle members to the development of probability theory and inductive
logic, the philosophy of logic and mathematics (apart from the guiding ideas of Carnap)
and to the philosophy of individual empirical sciences (physics, biology, psychology,
social science), cannot be discussed at all (see Creath and Friedman forthcoming and
Richardson and Uebel forthcoming for relevant essays). Even though the formalist
project became identified with mainstream logical empiricism generally (consider its
prominence in confirmation theory and in the theory of explanation), it was not
universally subscribed to in the Vienna Circle itself.
Concerning the criticism of the circular nature of the definition of analyticity, Carnap
responded that it pertained primarily to the idea of analyticity in natural language
whereas he was interested in "explications" as provided by the logic of science (or better,
a logic of science, since there existed no unique logic of science for Carnap). Unlike the
logician of science Carnap, who left it to psychology and brain science to determine
more precisely what the class observational predicates were that could feature in
protocol statements (1936/37), the empirically oriented meta-theoretician of science
Neurath was concerned to encompass and comprehend the practical complexities of
reliance on scientific testimony (see Uebel 2005). scientific theories, Theoretical Terms
and the Problem of Realism Yet even if it be conceded that the members of the Vienna
Circle did not harbour reductionist ambitions, the question remains open whether they
81
were able to deal with the complexities of scientific theory building. Here the prominent
role of Schlick must be mentioned, whose General Theory of Knowledge (1918, second
edition 1925) was one of the first publications by (future) members of the Vienna Circle
to introduce the so-called two-languages model of scientific theories. Note that the issue
of Realism vis-à-vis Theoretical Terms is closely related to two other issues central to
the development of Vienna Circle philosophy: Carnap's further attempts to develop a
criterion of empiricist significance for the terms of the theoretical languages of science
and his attempts to defend the distinction between synthetic and analytic statements
with regard to such theoretical languages.
A term is relatively significant if and only if there exists a statement in the theoretical
language that contains it as the only non-logical term and from which, in conjunction
with another theoretical statement and the sets of theoretical postulates and
correspondence rules, an observational statement is derivable that is not derivable from
that other theoretical statement and the sets of theoretical postulates and correspondence
rules alone. Yet when Carnap offered the Ramsey method as a method of characterizing
the "empirical meaning of Theoretical Terms" it was not their empirical significance as
such but the specific empirical import of Theoretical Terms that he considered (1966,
Ch. But it would be wrong to say that "RTC → TC" specified the meaning of these
Theoretical Terms; rather, "the A-postulate states that if entities exist (referred to by the
existential quantifiers of the Ramsey sentence) that are of a kind bound together by all
the relations expressed in the theoretical postulates of the theory and that are related to
observational entities by all the relations specified by the correspondence postulates of
the theory, then the theory itself is true. What tells against Carnap's project on its own
terms is that ramseyfication trivializes the truth of physical theory in the manner
indicated: the empirical meaning of Theoretical Terms that Carnap sought to capture
simply evaporates (Demopoulos 2003). If the reconstruction of empirical theories by
ramseyfication in Carnap's fashion is unacceptable, then all explications that build on
this are called into question: explications of theoretical analyticity as much as
explications of the experiential import of theories.
So the suggestion that the criterion of empirical significance can be regarded as a
proposal for how to treat the language of science cannot be brushed aside but for the
persistent neglect of the philosophical projects of Carnap or the non-formalist left
Vienna Circle. For instance, it has been argued (Carus 1999) that Carnap correctly did
not understand Tarski's theory of truth as a traditional correspondence theory such that
truth consisted in some kind of agreement of statements or judgements and facts or the
world where the latter make true the former. Much confusion exists concerning the
Vienna Circle and history, that is, both concerning the Vienna Circle's attitude towards
the history of philosophy and science and concerning its own place in that history.
Importantly, the explications given can be of two sorts: the formal explications of the
logic of science by means of exemplary models of constructed languages, and the more
informal explications of the empirical theory of science given by spelling out how
certain theoretical desiderata can be attained more or less under practical constraints.
Non-justificationism, that is, the theory that no theory can be proven, is at least as old as
Socrates, but Popper's version of it is the first that also purports to explain the growth of
knowledge.
On a justificationist theory of the task of the philosophy of science such as
Reichenbach's, which was identical to Popper's theory as he wrote Die beiden
82
Grundprobleme without chapter 5, science should be demarcated by the proper
assignment of truth values: science is the set of sentences with justifiably assigned truth
values. On the theory presented in Die beiden Grundprobleme without chapter 5, after
science had done its job, there were still, on the one hand, some fictions which ought to
be deemed scientific such as the theories of the Würzburg school in psychology and,
perhaps, as he said later, Einstein's physics, and, on the other hand, other fictions which
should be deemed unscientific, such as the psychologies of Freud and Adler. But Popper
had at that point no non-justificationist theory of rationality in general; his theory
applied to science alone. The conflict between Popper's new theory of science and his
older theory that only proven or refuted sentences can take truth values was removed by
Tarski. Tarski did not necessarily offer Popper an adequate theory of truth for his
philosophy of science.
After his meeting with Tarski, he was free to develop his fallibilist theory of science in
new ways, because he could claim that theories could be true even though there was no
proof of them. I begin with Agassi, who developed Popper's philosophy piecemeal and
then turn to Bartley who attempted to give critical rationalism a comprehensive
statement, that is, a version of it which would explain how a critical rationalist could
adopt a critical stance toward any idea whatsoever, including its own claims. He did this
by extending Popper's theory of the methods of scientific practice to include the critical,
and thereby progressive, use of metaphysical theories to guide scientific research. For,
he argued, on the one hand, the theory of rationality as proof should itself be proven, but
in fact it is not provable, whereas, on the other hand, the theory of rationality as
readiness to appraise theories critically should itself be open to criticism, and this is
quite possible. It is then no longer the case that the adoption of a rational approach to
problems is no more rational than commitments to belief systems, such as those of some
religion: the theory that rational practice means holding all theories open to criticism,
may itself be held open to criticism.
Like many, Popper wanted the theory of science to describe science, but he hardly tried
to apply his view to the history of science. The researches mentioned so far grew
directly out of Popper's non-justificationist theory of science. Mario Bunge developed a
non-justificationist theory of science, especially of physics, before he had ever heard of
Popper, and he does not view his work a part of the project known as critical rationalism.
He has effectively bolstered Popper's arguments against attempts to use induction to
establish any degree of probability of any theory and effectively criticized Popper's
theory of verisimilitude. On Miller's view it seems a person can declare true any
unrefuted theory, say a minimal astrological theory, or Descartes' theory that souls have
no extension, without violating any rationalist precept.
Their peculiarity is that they seek methods of selecting credible theories or the best
theories, while recognizing the validity of the criticisms of methods of justification
launched by critical rationalists. Unlike Musgrave, he realizes that Popper's theory of
corroboration cannot serve this purpose, as it allots the least probable theories, the ones
that take the most risks, the highest degree of corroboration. Watkins views himself as a
critical rationalist even though he stresses corroboration, because he does not relate
corroboration to appraisals of the truth or probability of theories, but rather to other
good qualities of theories. This effort began with Agassi's criticisms of Popper's rule to
always prefer the theory with the highest degree of testability: Sometimes a testable
theory has a higher explanatory power than some competitor, he argued, but also has a
83
lower degree of testability than this competitor. John Wettersten has continued critical
rationalist studies in the sociology of science with examinations of how adventurous
and conservative styles of research complement and compete with each other, how
stylistic standards can hinder research, how a problem-oriented approach may improve
standards in science and technology, and how critical rationalism may be used to guide
sociological research.
Wettersten has developed critical studies of alternative approaches to the sociology of
science: a critical rationalist approach aims at minimizing the idealization of science,
but without explaining scientific knowledge away. I.C. Jarvie has recently studied how
and when Popper added a theory of the institutions of science to his theory of the logic
of science (Jarvie 2001) . Watkins pointed out that Popper's theory offered a basis for a
pluralistic society which traditional theories of rationality cannot: justificationist
theories allow only one view to be justified given the evidence at any time, whereas
critical rationalism allows for a range of defensible theories which may democratically
compete in the political arena. As a consequence, critical rationalists such as Jeremy
Shearmur and Gerard Radnitzky have attempted to pull Popper's theory toward Hayek
and laissez-faire economics, whereas others, such Malachi Hacohen, Agassi and Helmut
Schmidt have found in his theory a framework for theories of active social reform.
There is ongoing research to develop a critical theory of the history of philosophy, of
the sociology of science, of political philosophy, of ethical theory, and of social and
political institutions.
84