Feb.6, 2004
Chapter 4: Revolutions and Rationality
Inductivism
Naïve: Bacon
Sophisticated:
Logical positivists:
Vienna Circle: Schlick, Hahn, Carnap, Feigl (1920s-30s)
Berlin: Reichenbach, Hempel
Logical empiricists:
U.S.: Carnap, Feigl, Reichenbach, Hempel (1940s-60s)
Falsificationism: Popper (1930s-70s)
Social Constructivism: Kuhn, Feyerabend (1960s-…)
The sophisticated inductivists use the distinctions between context of discovery
and context of justification.
The logical positivists were mostly Jews and socialists living in Austria (Vienna
Circle) and Germany, and so they got disbanded with the rise of the Nazis (1930s). They
either died or fled to Britain and the US. Those who fled to the US happen to live longer
and became the logical empiricists.
Philosophically, the difference between them and the logical positivists is that
they reject verificationism (the only meaningful statements come from observation or
logic, because they are the only ones that can be verified), and eventually accept that
observations are theory-laden. The logical empiricists represented the dominant view of
science.
Difference between Popper and the sophisticated inductivists
1. The problem of induction: Popper thinks that confirmation is impossible. The
sophisticated inductivists think that it can be solved by developing a precise
logic of confirmation.
2. The demarcation problem: the positivists adopt the verificationism thesis,
saying that the only meaningful statements are those which can be confirmed:
their meanings are the means by which they can be confirmed.
For Popper, any falsifiable statement is scientific. Unfalsifiable statements are
not, regardless of their logical status. Still, unfalsifiable statements are not
meaningless.
E.g., a tautology is meaningful and scientific for the positivists, but not
scientific for Popper. God exists is meaningless for the positivists, but
meaningful for Popper, although not scientific.
4.1 The received view of science
Still, Popper and the sophisticated inductivists have a lot in common:
1. Science is cumulative: there is a steady growth in our knowledge of the world as
scientists build on the achievements of their predecessors. Compare with art,
literature, and philosophy.
2. Science is unified: there is a single set of fundamental methods for all the
sciences, and the natural sciences are ultimately reducible to physics.
Reductionism: since everything is made of the same stuff (atoms, etc.), the laws
of biology ought to be derivable from those of chemistry, and those of chemistry
from the laws of physics.
3. There is an epistemologically crucial distinction between the context of discovery
and the context of justification. The context of justification is what matter in
evaluating a theory, not the context of discovery.
4. There is a value-free logic of confirmation or falsification implicit in all scientific
evaluations of the evidence from some hypothesis. They are value-free in the
sense of being independent of the personal non-scientific views and allegiances of
scientists.
5. There is a clear demarcation between science and non-science.
6. There is a sharp distinction between observation and theory. Thus, observation
and experiment is a neutral foundation for the testing of scientific theories.
7. Scientific terms have fixed and precise meaning.
4.2 Kuhn’s revolutionary history of science
In his book The Structure of the Scientific Revolutions (1962), Kuhn looked at the
history of science, in particular the Copernician revolution. He noticed that the standard
historical accounts of scientific discoveries found in textbook often simplify and distort
the real stories of theory development and change. This is because these summaries are
intended to motivate and justify contemporary theories, more than they are intended to be
faithful to the complexities of history. Kuhn makes an analogy: the accounts in textbook
are to the real history of science what a tourist guidebook is to what a country and its
culture are really like. Only the favoured aspects are featured, and the rest is neglected.
Kuhn used his analysis of the history of science to conclude that the abandoned
beliefs about the world, like the Aristotelian view, were produced and held for the same
kind of reasons than our current scientific theories, and so that our abandoned beliefs are
no less scientific than what is taught and learned in the universities today.
He also suggests that history does not show a steady accumulation of knowledge,
but rather often involves the wholesale discarding of past theories.
Furthermore, he endorses the Duhem-Quine problem (i.e., when experiment
conflicts with a scientific theory, logic alone does not tell us which of the components of
the theoretical system is at fault) and argues that there is therefore the choice is
influenced by the historical context and the personal inclinations of the scientists
involved. Thus, there is no single logic of theory testing, and science is never theoryneutral and objective.
In short, Kuhn goes against 1, 2, 3, 4, 5, 6, and we will see later that he also goes
against 7.
4.3 Paradigms and normal science
The most fundamental concept of Kuhn’s philosophy is that of paradigm. There
is no clear definition of it; some people have argued that we can find as many as 52
different meanings of ‘paradigm’ in Kuhn’s book. In any case, there are two main
meanings: paradigm as a disciplinary matrix, and paradigm as exemplar.
Kuhn argues that doing science requires an agreement among scientists about the
kind of things that exist in the universe, what kinds of questions it is legitimate to ask
about these things, and which methods can be used to answer these questions.
A disciplinary matrix is a set of answers to such questions, which will be learned
by scientists as they are trained to be scientists. Not all of these answers are explicit:
some parts of it are constituted by the shared values of scientists (like preferring some
kinds of explanations over others), and others are practical skills and methods not
necessarily expressible in words (tacit knowledge).
Exemplars, by contrast, are the instances of good science that are taught to
students. Textbook are full of standard problems and their solutions, and students are
given exercises that requires them to adapt the techniques used in the examples to new
situations. Exemplars are part of the disciplinary matrix of a science.
- Example of the paradigm (first sense) of Newtonian physics (p.99-100).
Cycle of science
Most science is what Kuhn calls ‘normal science’, because it is conducted within
an established paradigm. The scientists’ job is to extend the application of the paradigm
to other domains by making lots of observations of increased precision, which often
involves creating new instruments, and making all these new observations fit with the
paradigm.
During normal science, scientists do not question the fundamental principles of
their discipline. They do not do as Popper advocated, and reject their theory as soon as
some evidence against it is found. Rather, they stick to it and try to accommodate the
facts with the theory, if possible. In any case, they will tolerate a fair number of
anomalies before starting to think that something is wrong with their theory.
However, sometimes scientists find anomalies that won’t go away, and that are
just too big or numerous to be ignored. At this point, some scientist (especially the
younger or more daring) will begin to question some of the basic assumptions of the
paradigm, and maybe suggest some alternatives. If successful research within the
paradigm also begin to decline, more and more scientists will focus on the anomalies, and
eventually the general perception will be that the paradigm is in ‘crisis’.
Crises are rare, according to Kuhn, for paradigms do not become established
unless they are pretty robust and able to accommodate vast majority of the phenomena in
their domains.
Eventually a crisis will be resolved, often by the adoption of a new paradigm
which resolves the problems associated with the previous one. This is a scientific
revolution. In a scientific revolution, the old paradigm is abandoned wholesale in favour
of the new one.
Important: 1) The new paradigm does not merely add some assumptions to the old
paradigm, but rather totally replaces it. 2) Also, an old paradigm is abandoned only if
there is a better one available to take its place.
Then scientists go back to normal science, this time using the new paradigm.
For Popper, scientists are perpetually in a state of potential revolution, since they
should always be ready to reject their theory. For Kuhn, revolutions are rare events, as
scientists are quite committed to their paradigm. Popper saw such commitment as an
anti-scientific attitude (Maxists, psychoanalysts).
Kuhn argues that the values and personality of scientists play an important role in
determining whether or not they will accept a new paradigm.
E.g. Einstein’s realist
outlook made him adverse to quantum mechanics. Other factors: Conservative or risktakers; good position or temporary contract; who are your teachers, students, colleagues.
Paradigms are the intellectual property of social groups, and so what influence
paradigm creation and adoption are whatever impact human behaviour and choice. In
Kuhn’s view, science must be seen in its social and historical context. As Lakatos puts it:
“according to Kuhn scientific change – from one paradigm to another – is a mystical
conversion which is not and cannot be governed by the rules of reason: it falls totally
within the realm of (social) psychology of discovery.
4.4 The Copernician revolution
An example of paradigm shift:
In about 150 years, we went from the geocentric view of Ptolemy, backed by the
Aristotelian worldview and the Catholic Church, to the heliocentric view of Copernicus,
as modified by Galileo and explained by Newton. Today it seems like the heliocentric
view is obviously better than the geocentric one, a triumph of reason over dogma, but
Kuhn argues that at the time it was not obvious at all.
Things in favour of Ptolemy’s view:
1) Fits the observation that we do not feel the earth to be in motion and planets and
stars seem to move around it.
2) Offers a reasonably accurate means of predicting the motions of the planets which
was successfully used for centuries.
3) That the earth is at the center of the universe fits well with the idea that it was
specifically created for us by God.
4) Allows Heaven to be located literally above the Earth.
5) It is compatible with Aristotle’s account of the natural motions of the heavenly
bodies, which give a neat explanation of what we can observe in the sky.
Reasons 1 and 2 are based on empirical experience, and reasons 3-5 are based on the
compatibility of Ptolemy’s view with other strongly held views.
For centuries people used Ptolemy’s view, along with Aristotelian physics, to
explain and predict the motion of planets and stars. This was a time of normal science.
This paradigm faced some anomalies because the orbits of the planets did not
seem to be perfect circle, as the theory predicted. However, it was possible to
accommodate this fact by using epicycles to modify the main circle so that the resulting
orbits fit with observations. Again, this fits normal science: as astronomers gather more
precise data, some of which does not fit the paradigm, rather than rejecting the basic
assumptions of the paradigm, they modify a bit their theory to fit the data. This provides
an ongoing research program for astronomers.
So, as an astronomer working under Ptolemy paradigm, your job is to make ever
more precise observation of the paths of planets, and to add epicycles where needed to
make the theory fit with the observations.
But the anomalies build up. The complexity and the number of competing
versions of the Ptolemaic theory increase. This, along with increasing social pressure for
calendar reform, leads to the perception that the paradigm was in crisis. But this is not
enough to lead to a revolution, for there are no suitable alternative.
Enter the Copernician view, supported by people like Kepler, Galileo, Descartes,
and others.
Things in favour of the Copernician model:
1) Mathematically simpler
2) After Kepler published his laws of motion (but only after), the heliocentric view
became a significantly more empirically adequate theory.
Problems:
1) Initially, Copernicus’ theory was no more accurate than Ptolemy’s.
2) Some predictions of the model are not observed:
a) Venus should sometimes appear six times as large as other time, because
sometimes the Earth and Venus are on the same side of the sun, and
sometimes on opposite side. This was not observable with the naked eye.
(This was later observed with telescopes, but not at Copernicus’ time)
b) The model predicts a stellar parallax effect (the stars should appear to
move, depending on which side of the Sun we are), which was not
observed by using the most accurate instruments available at the time.
3) There are (apparently) good arguments against it:
a) The “tower argument”: if the Earth is moving and I drop a stone from the
top of a tall tower, the stone should move some distance away while she
falls. But in fact the stone will be at the same distance from the tower than
when I dropped it.
b) Why are not objects on the surface of the Earth thrown off the Earth, like
objects on the rim of a wheel are when you spin it?
c) Why does not the Earth leave the Moon behind, if it moves?
4) Does not fit well with theology (location of Heavens; somewhat at odds with the
idea that Earth was created specifically for us)
5) Contradict the best physics of the time (i.e., Aristotle’s).
Kuhn therefore argues that those who accepted the Copernician view had no good reason
for it, but were rather influenced by their personality and other considerations, like
whether you favour mathematical simplicity or prefer coherence with the overall worldview and conformity to common sense. Thus, the change of paradigm is not a purely
rational matter. For instances:
-
Copernicus prized mathematical simplicity, and had the mathematical ability to
formulate the heliocentric alternative precisely.
-
Galileo was enough of a rebel to take on the Church, even when the consequences
for his life were unpleasant. (Though he eventually backed off)
-
Kepler had a mystical belief in the basic mathematical harmony of the natural
world which made him prefer simple elliptical orbits to complex circular ones,
and he had access to more detailed astronomical data than anyone before him (he
got them from Tycho Brahe).
-
Descartes had developed a physics that was radically different than Aristotle’s,
and had an explicit philosophical agenda that went much beyond the available
data.
Is science irrational then?
4.5 Theory and observation
Real example of influence of theory on observation (also called ‘theory-ladenness’):
Sunspots: patches of different brightness on the surface of the Sun. Never
recorded in Europe before the Copernician revolution, yet well known to Chinese
astronomers for centuries beforehand. The belief that the Heavens are perfect and
unchanging seems to have prevented the Europeans o notice such an obvious example of
changeable extraterrestrial phenomenon.
This threatens to undermine the objectivity of scientific testing, because if all
observations are contaminated by theories, then observation cannot be the neutral arbiter
between competing theories, which is what the received view says it is.
Also, when do we observe something, rather than infer it?
Do we really see the wind, or do we rather simply see leafs floating and umbrella
flip upside-down, and so on, and infer the presence of the wind?
Do we observe electricity in the lighting of a bulb, or are we simply seeing the
light, and infer the presence of electricity?
Paul Churchland suggests that two individuals can look at the same stimulus and
literally see two different things, if their theory of what they are seeing is different.
However, Jerry Fodor replies that these two individuals will see the same thing,
but will differ in their interpretation of it. In other words, he makes a distinction between
“seeing” and “seeing that” (p.114). Looking at a glass of water, they will both see the
glass, but if one of them has never heard of a glass of water before, he will not see that it
is a glass of water, only the other will. Still, the one who has never seen nor heard of a
glass of water before will still see it, as shown by the fact that he picks it up in curiosity.
To sum up, it is probably true that our theories have an influence on our
observations. But is this influence so great that it prevents us from ever proving or
disproving a theory?
4.6 Incommensurability
If Kuhn is right that our criteria of what constitute good science depends on the
paradigm we adopt, then there is no neutral way to compare two different paradigms.
Rivals paradigms are incommensurable, that is, they have no common measure.
One common way to interpret this feature of Kuhn’s theory is that it implies that
scientific progress is in fact no progress at all but only change motivated by purely
psychological factors. In other words, the ‘truths’ of scientific theories are determined in
whole or in part by social forces (relativism about scientific knowledge).
The incommensurability of competing paradigms is supported by the theoryladenness of observation: if all observations are influenced by background theories, then
we cannot use experiments to decide which paradigm is better, because the supporters of
one paradigm will not agree with the supporters of the other paradigm about what is
being observed.
For Kuhn, the change from a paradigm to another is holistic, which means you
have to fully endorse one or another. One can never accept two rival paradigms at the
same time, nor bits and pieces of one, and bits and pieces of the other.
This feature trickles down to the specific theories or laws included in a paradigm,
and even to the terms and concepts. The idea is that scientific terms get their meanings
from their place in the structure of a whole theory. Thus, when there is a change of
theory, even if a given term (e.g., force) is kept in the new theory, its meaning will be
different.
For example, in Newtonian physics, ‘mass’ is an intrinsic feature of objects which
is divided in two kinds: inertial and gravitational. With Einstein’s theory of relativity,
there is only one kind of ‘mass’, and it is a form of energy (from e=mc2 you get m=e/c2).
This means that the terms and concepts of scientific theories are not translatable
from one paradigm to another. This is called meaning incommensurability.
Also, what we refer to by the use of a given term (i.e., the objects we are talking
about) will change under different paradigms. This is called reference
incommensurability. Thus, two theories about atoms are not referring to the same
objects. Thus, by changing our theory we did not improve our knowledge of atoms,
because we are no longer talking about the same thing. This is bad news for realists,
those who think that the objects to which our scientific theories refer to really exist in the
world.
Kuhn says: “when paradigms change, the world changes with them.” (p.118)
Thus, what the world actually is depend on our theory about it. Thus, Ptolemy was not
wrong to think that the Earth is that the center of the universe, nor was Galileo wrong to
think that the Earth turns around the Sun, for the Earth of Ptolemy and the Earth of
Galileo are not the same object.
4.7 Relativism and the role of reason in science
So is science totally irrational?
Even if we do not think so, it is very difficult to find a description of a scientific
method which would make science rational, yet provide a good account of the history of
science.
In his later work, Kuhn sought to distance himself from the most extreme view
given absolutely no role to rationality in science. He suggested that there were five core
values common to all paradigms:
-
A theory should be empirically accurate within its domain.
(But Kuhn pointed out that scientists will tolerate a lot of inaccuracies before
renouncing to a paradigm. When are accuracies too many?)
-
A theory should be consistent with other accepted theories.
(Was Ptolemy’s view better than Copernicus’, because Ptolemy’s fitted with
Aristotelian physics and theology?)
-
A theory should be wide in scope and not just accommodate the facts it was
designed to explain.
-
A theory should be as simple as possible.
(But maybe the world is not simple. Maybe the true theory is the messy one.)
-
A theory should be fruitful in the sense of providing a framework for ongoing
research.
(But if we ever found the true explanation of a phenomenon, eventually we will
know everything there is to know about it, and there will be no more research
possible on it. Should we then change of theory?)
Thus, science is not completely irrational, since there are some limits on what scientists
should accept.
See any problems with these values? (See parentheses above)
Not sufficient to determine which paradigm should be accepted for any interesting
case. These values may be in conflict with one another, or subject to interpretation (e.g.,
what does it mean to be ‘simple’?)