Problems of Empiricism: First Essay
Wylie Breckenridge
Explain the difference between reductionism and instrumentalism
about theoretical entities. What do these views agree about? What do
they disagree about? Why is the theory/observation distinction
important for anti-realists about scientific theories? Does it make a
difference what kind of anti-realist you are; i.e., does the severity of
the problem depend upon whether you are a reductionist or an
instrumentalist?
Scientific theories are a problem for empiricists. They are arguably our most successful
and reliable sources of knowledge, and yet they don't seem to satisfy the empiricist
requirement that all of our knowledge be about, and justified through, experience. Antirealism is an attempt to solve this problem. Its proponents claim that science, despite
how it seems, really is grounded in experience and therefore is an empirically valid
source of knowledge.
For the empiricist, the only things that we have direct access to are our sensual
experiences. They are all that we can talk meaningfully about, and they are all that we
can know. The empiricist thinks of this experience as being presented on an 'internal
screen', and if there is a world external to us then it can only be known as we 'observe' it
on this screen. Empiricists differ in opinion as to what the basic components of this
experience are. Phenomenalists claim that they are individual sense-data - patches of
colour, snippets of sound, etc. Medium-sized object empiricists claim that they are
bundles of sense-data - the ones we call chairs, tennis balls, etc. Each of these
empiricists has his own language of experience - the language from which all
meaningful and knowable statements are composed. For the phenomenalist this
language is the language of sense-data. For the medium-sized objectist it is the language
of medium-sized objects.
Many scientific statements are not expressed in either of these languages. The statement
"all rocks sink in water" is expressed in the language of medium-sized objects, but not
in the language of individual sense-data. But the statement "electrons have a mass of
9.11 x 10-31 kg" is expressed in neither. For the empiricist, this statement is meaningless
- it is not about anything that we can observe on our internal screens - or if it does have
any meaning it is not a claim whose truth or falsity we can verify because, again, we
cannot observe what it claims. Thus the empiricist is obliged to reject this as an empty
claim, and much of science along with it. In response to this, the anti-realist argues that
scientific statements should not be taken at face value, and that when correctly viewed
they do indeed meet empirical requirements. There are two principal versions of antirealism: reductionism and instrumentalism. I will explain each position in turn.
In what follows I will talk about two distinct subsets of any scientific language. The
first, called the observation language, contains all those statements that are expressed in
the language of experience as agreed upon by empiricists. For the phenomenalist, this
will be the language of individual sense data. For the medium-sized object empiricist, it
will be the language of medium-sized objects. The rest of the scientific language I will
call the theoretical language. It is theoretical in the sense that it contains words and
phrases that are only meaningful in the context of the particular scientific theory. The
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observation language, on the other hand, is supposed to be meaningful as it stands,
independently of the theory in which it appears. It is important for the empiricist to
make a distinction between these two languages, because on their view it is only the
statements that are expressed in the observation language that make meaningful and
verifiable claims. Thus it is important for the empiricist to specify exactly what this
language is, or else she will not be clear about what the theory is actually claiming. I
will refer to statements in the observation language as observation statements, and to
statements in the theoretical language as theoretical statements.
It is the theoretical statements that pose the problem. According to the empiricist they
are meaningless and/or unverifiable, and so add no empirical content to the theory. But
they seem to be essential to it - not only is much of the theory expressed in terms of
them, but many predictions about what observational consequences follow from what
observational premises seem to rely essentially upon them. So if the empiricist wants to
keep scientific theories as a genuine source of knowledge, then she must give us an
account of their use of theoretical statements.
The reductionist claims that they are just a shorthand way of expressing a factually
equivalent class of observation statements and that they can, if so desired, be translated
into the latter. It is through this class of observation statements that the theoretical
statement gets its meaning, and it is through these observation statements that its truth
or falsity can be verified. What the reductionist is claiming, in effect, is that a scientific
theory can be completely expressed in the observation language, without losing any of
its content. For example, consider the following theory:
All rocks contain sinkitons
Anything that contains sinkitons sinks in water
Even for a medium-sized objectist these statements are theoretical - they are not
expressed in the language of experience, because of the reference to (as yet)
unobservable 'sinkitons'. The reductionist claims that that these two statements are just a
shorthand way of writing an equivalent class of observation statements. We can see that,
taken together, they are factually equivalent to this single observation statement:
All rocks sink in water
(In this case they are not really shorthand at all - the equivalent class of observation
statements is smaller. But this would probably not have been true for a more realistic
example.)
The instrumentalist claims that theoretical statements are not really statements at all,
and so any requirement of meaning or factual content is misguided. He claims that they
are not the kinds of things that can be true or false - they are just rules for deducing
observation statements from observation statements. Consider the above theory again.
One way that I can use this theory to predict that if W is a rock, then W sinks in water is
as follows:
1. W is a rock
2. All rocks contain sinkitons
3. Anything that contains sinkitons sinks in water
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premise
premise
premise
4. W contains sinkitons
5. W sinks in water
1,2, modus ponens
3,4, modus ponens
Here I have used the theory as premises and derived the conclusion by two applications
of modus ponens. The conclusion will be true as long as the theory is true. The
instrumentalist claims that this is the wrong way to use the theory. It is not a pair of
factual claims that can be used as premises in a deduction - they are rules of deduction
in themselves. He would present the argument like this:
1. W is a rock
2. W contains sinkitons
3. W sinks in water
premise
1, all rocks contain sinkitons
2, anything that contains sinkitons sinks
Note that this deduction contains an intermediate theoretical statement, "W contains
sinkitons". The instrumentalist claims that this is not a factual claim, nor is it a rule of
deduction, but is a kind of place-holder that aids the deductive process. An analogy
sometimes used to explain instrumentalism is that theoretical statements are to scientific
theories as hammers are to carpentry. Hammers are merely a tool for turning raw
materials into finished products, not materials or products themselves and hence only of
instrumental value to the carpenter. I think it's more accurate to divide theoretical
statements into those that the instrumentalist thinks of as deductive rules ('All rocks
contain sinkitons') and those that he thinks of as place-holders ('W contains sinkitons').
Then in the carpentry analogy it is the latter that correspond to the hammer, with the
former corresponding more to a set of instructions for using the hammer.
This is how reductionists and instrumentalists account for the use of theoretical
statements - the former by claiming that they are meaningful and verifiable once they
have been translated into equivalent observation statements; the latter by claiming that
they are not supposed to have meanings or to be factual claims at all. Both can say,
therefore, that in keeping with empiricist requirements all the factual claims of a theory
are really about matters of experience and nothing beyond.
But they run into trouble elsewhere. To see why, I will consider one problem that is
faced by each of the four types of empiricist that I have mentioned - the reductionist
phenomenalist, the reductionist medium-sized objectist, the instrumentalist
phenomenalist, and the instrumentalist medium-sized objectist.
The reductionist phenomenalist claims that every statement of a theory can be translated
into equivalent statements about sense-data. But it is not obvious that this is possible,
even in principle. To see how difficult it is, one only has to attempt this translation for a
statement like "there is an apple on the table beside me". It takes a great deal of practice
to be able to isolate individual patches of light and colour from the overall scene, and
even then it is a difficult process. Nagel discusses this problem and concludes as
follows:
In short, the "language" of sense data is not an autonomous language. And
no one has yet succeeded in constructing such a language. However, if there
is indeed no such language, then the thesis that all theoretical statements
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are in principle translatable into the language of pure sense contents is
questionable from the outset.1
The reductionist medium-sized objectist does not face this problem, but he faces another
(and one that also faces the phenomenalist). It is claimed that a given theoretical
statement can be translated, without loss of content, into a class of observation
statements (whatever the observation language may be). To ensure that no content is
lost, then, the class of observation statements must contain all of the observational
consequences of the original theoretical statement. But consider a statement like "there
is a net electric charge on this plastic ruler". The consequences of this, within the theory
of electromagnetism, include things like "if such-and-such an object is placed in suchand-such a place then so-and-so will happen". There will be a statement like this for
every object that is effected by an electric charge, and for every position in space around
the ruler. Thus the set of equivalent observation statements will be infinitely numerous.
Worse still, we may discover in the future that a type of object previously thought to be
unaffected by electric charge is actually affected by it, and so we must include in our
translation statements about the behaviour of these objects as well. That is, not only is
the class of observation statements vast but it is also impossible to specify completely at
any point of time. A similar problem is suggested by Craig's theorem. This is a result
from formal logic that initially appears to lend support to the reductionist thesis. In a
nutshell it says that if the sentences of a deductive system, including its axioms, are
partitioned into two types (think of them as the observation statements and the
theoretical statements) then we can replace it with a new formal system whose axioms
are made up just of observation statements and such that both systems have the same set
of observation statements as deductive consequences of the axioms. In effect it is saying
that the reductionist program is achievable in the case of a formal language. Scientific
language, however, does not meet the requirements of a formal language, and so the
relevance of Craig's theorem to the reductionist thesis is questionable. Moreover, the
procedure involved in forming the new deductive system only works if all of the
deductive consequences of the old system are known in advance, and these
consequences are all presented as axioms in the new system. If we apply this to a
scientific theory, then, it says that we can only remove the theoretical statements from
the theory if we know all of their observational consequences in advance, and then all of
these will reappear as axioms.
Any survey of the statements of a scientific theory will make it clear that very few, if
any, are expressed in the language of sense-data. The instrumentalist phenomenalist,
then, is forced to claim that the theory has no factual content at all - that the theory is
just a set of rules and tools of deduction, and that it contains no factual premises to
deduce any factual consequences from (remember, he does not require that any
translation of statements into the language of sense-data should take place - he just takes
the statements as they are). This is clearly not a desirable position.
On the other hand, theories do contain statements that are expressed in the language of
medium-sized objects, and so the instrumentalist medium-sized objectist is not faced
with an account of the theory that renders it empirically empty. But he faces another
potential dilemma. Consider the theory about sinkitons presented above. Apples are a
part of our medium-sized object language because they are a familiar feature of our
daily experience. Sinkitons are not, because we haven't yet observed them and we
1
Nagel, p. 122.
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haven't any idea what they might look like if we did. The instrumentalist is thus obliged
to say that the statement "All rocks contain sinkitons" is not a statement at all, but a rule
of deduction within the theory. Suppose something changes so that we can observe
sinkitons, just as well as we can observe apples. Then sinkitons would become a part of
the medium-sized object language, and the instrumentalist is obliged to say that "All
rocks contain sinkitons" is now a factual statement and not a rule of deduction. The
change comes about because the observation language - the criterion by which we are
supposed to judge which statements are factual claims and which are not - has changed.
The instrumentalist has a choice - either fix the observation language once and for all,
and ignore any changes in what we can observe; or allow the observation language to
evolve, and continually reassess the factual content of the theory. Neither option is very
appealing.
It seems to me that both the reductionists and instrumentalists are doomed to face
problems because the account they give of scientific language does not agree with the
way that we typically use it. When I make a statement like "All rocks contain
sinkitons", I don't think of myself as really just talking about sense-data or other
bundles of experience, nor do I think of myself as really just stipulating a rule that can
be used to deduce matters of observation. I think of myself as making a claim about the
way things are - that there really are things called sinkitons with the properties
described. But in making this claim I am not committed to believing that it is true. In
fact, I am not even committed to being interested in its truth or falsity at all. Typically I
am more interested in its empirical adequacy - how will it agrees with what I observe.
And that might be enough to give empirical justification to my use of the theory. If antirealist theories about scientific language do not agree with what we actually observe in
the behaviour of practising scientists, then these theories are empirically inadequate and
therefore questionable.
I suspect that reflecting on the way that I actually think when I'm using a scientific
theory will not only show the inadequacy of the anti-realist account of science, but also
the inadequacy of the basic assumption of empiricism. That assumption is that
'observation' is the passive process of 'viewing' things as they are presented on my
'internal screen'. According to the empiricist, I am supposed to take this 'given' data and
from it construct all of my beliefs and knowledge. But it seems to me that often I
construct a theory first and then check it against the evidence available to me. Part of
this evidence comes from my senses, but a good deal of it comes from my other beliefs.
In fact, I suspect that I never observe my sensual experience at all, but only the final
products of an elaborate construction involving both the sense-data available to me and
my whole system of beliefs. In short, I suspect that the empiricist has got things around
the wrong way - experience is not something that precedes knowledge, but the way that
we present to ourselves the consequences of our beliefs. What we are viewing on our
internal screens is not what is happening 'out there', but what is happening 'in here'.
What I am experiencing is not an external world, but my internal world projected
outwards. These particular speculations may be unreasonable, but I think the suggestion
that we question the empiricist starting point is not.
Bibliography
B. van Fraassen, "Arguments Concerning Scientific Realism", in the course reader.
G. Maxwell, "The Ontological Status of Theoretical Entities", in the course reader.
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E. Nagel, The Structure of Science, Chapter 6.
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