Fodor's target in his article is the idea of the "unity of science" defended by the positivists and exemplified, for instance, in a major publishing project they called "The Encyclopedia of Unified Science." Their idea was that higher-level sciences could (and should!) be "reduced" to lower-level sciences, and ultimately to physics.
The picture was that the "special sciences" (i.e. all the sciences that aren't physics!) formed a natural hierarchy, with higher-level sciences reducing to lower-level ones. Like this:
We need to discuss what they meant by "reduced" or "reduction." There are at least three things one might mean. Fodor does not necessarily disagree with the first, but he does with the other two.
Reduction of individual things
It seems plausible (for the most part, I think!) that the particular things that the higher-level sciences talk about are composed of things at lower levels. So: societies are composed of individual people; individual people are composed of cells; cells are composed of chemical compounds; and chemical compounds are composed of atoms. If this is right, then every particular thing (i.e. token thing) is identical with some particular physical thing (or collection of things). This is essentially the token-token identity theory, generalized from psychology to all the special sciences. [side note 1: there may be problems about this too: a cell isn't just a collection of chemical compounds; they have to be organized in a certain way. Moreover, the way they have to be organized may need to be described in something other than the language of physics. So it may be unclear exactly what "reduction" means or whether it's true even at this level.] [Side note 2: Of course, a substance dualist will reject even this relatively harmless sense of reduction!]
Reduction of types
It is a separate question whether the kinds of things higher-level sciences talk about can be "reduced to" lower-level kinds of things.
There are two ways such "reduction" might go. First, higher-level types might be identical with lower-level types. This is what Kim calls identity reduction, and is closely related to the type-type identity theory.
Second, it might be that we can give a functional definition of higher-level types, and then find lower-level types which satisfy the functional definition. This is what Kim calls functional reduction, and is obviously closely related to functionalism. For example, we can give a functional definition of a mouse trap, and then find out which kinds of physical objects satisfy the definition.
For instance, in the case of genetics, it appears not just that particular (token) genes are identical with particular (token) strings of amino acids, but that in general for every type of gene there is a corresponding type of string of amino acids.
Reduction of laws
Ultimately what the positivists wanted was some sort of reduction of higher-level laws to lower-level ones. Fodor says that two things are required for a high-level law to be "reduced" in the relevant sense. (1) The types that figure in the high-level law must be reduced to lower-level types (as in "reduction of types," above). (2) There must be a lower-level law connecting the lower-level types to which the higher-level types were reduced. If both (1) and (2) hold, we can say that the higher-level law has been reduced to a lower-level one.
Reduction and the Explanatory Gap
If we can give a reductive explanation of consciousness, this would solve the problem of the explanatory gap.
Q: how can we explain why Jones is in pain on the basis of physical phenomena? (This is related to the question: why is pain correlated with neural state N?)
If we can give an identity reduction, then the correct answer is: there are no such correlations, and therefore there is no such gap. If mental phenomena are identical with neural phenomena, then it's false to say that they are correlated: they're just the same thing, so there isn't anything here that needs explanation. Similarly, we don't need an explanation for why Jones is in pain over and above the explanation of why he's in neural state N.
On the other hand, if we can give a functional reduction, then mental phenomena aren't identical with neural phenomena, but they are realized by them. But in this case, it appears that we have a genuine explanation of neural-mental correlations. The explanation goes something like this:
1. functional definition of mental type M: M is a state that is caused by . .
. and is related to other states by . . . and causes . . ..
2. scientific laws: neural state N is caused by . . . and is related to other
states by . . . and causes . . ..
3. Jones is in N
Therefore, 4. Jones is in M
This looks like an explanation of why Jones is in M, provided that we can fill in the details. (The problem is in finding the functional definition mentioned in 1!)
Last update:
October 5, 2011.
Curtis Brown | Philosophy of Mind | Philosophy Department
| Trinity University
cbrown@trinity.edu