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Why Disjunctions Can Figure in Laws?
Loewer 2007a[1] argues for a Non-Reductive Physicalism (NRP) as contradistinguished from plain old Reductive Physicalism (RP). This is something of a family quarrel to begin with because both sides seem to agree that dualism is out and mentation supervenes on a purely physical substrate.
In particular, Loewer considers and dismisses a line of thought that threatens to show that NRP is unstable and thus not a coherent alternative to RP.
Suppose that M is a mental property and occurs in some law, say M →R (the law may be a ceteris paribus law) and so is a G-property. Suppose that physicalism is true. Wont there be some … physical property Q constructed out of physical genuine propertiesi.e. a disjunction of physical properties or configurations of physical propertiesthat is coextensive with M in all physically possible worlds? But then wont it be the case that Q →R is also a law? If so, it follows that Q is a G-property since it figures in a law. If this is correct, then NRP comes very close to collapsing into RP since either M = Q or M* = Q where M* is the property M restricted to the class of physically possible worlds. In the first case RP holds; in the second case it is close enough to make the difference between RP and NRP look awfully trivial.
Loewer offers two counterarguments. The first is one that he dismisses out of hand because, he says, it looks a lot like declaring victory and withdrawing:
If any construct out of physical properties that is coextensive (or coextensive in every physically possible world) with a G-property counts as a P-property then indeed NRP and RP come to much the same.
The problem he says is that
considerations involving functionalism and externalism show that Q will have an enormously complex characterization in terms of physics and plausibly has no characterization in terms of any of the special sciences.
In effect, Loewer invokes Occams razor, which says; Simpler is better; dont complicate things unnecessarily. In so doing, Loewer is following Fodors argument that complex (and sometimes potentially unbounded) disjunctions of physical properties are not natural kinds. As Loewer summarizes Fodor, the problem is that the disjunctive properties at issue need not be kinds, and
disjunctions of physically heterogeneous properties are not kinds of physics. [Fodor] seems to mean by this that the various [properties] can be realized by various configurations of physical entities that are made from different materials.
On the other hand, although the disjunction of the realizers of F may be physically heterogeneous (and so not a kind of physics) they may be psychologically homogenous so that F is a kind of psychology. If F is a functional natural kind of psychology its instances are psychologically homogeneous since they share the same psychological role.
Although Fodor doesnt say this he might add that psychological properties and laws may obtain even in worlds whose fundamental properties and laws are very different from those of the actual world. In these worlds psychological properties are realized by alien fundamental properties and psychological laws by alien fundamental laws.[2]
Yates 2005[3] analyzes Fodors cavil as (I think properly) a question of gerrymanderedness rather than disjunctiveness or heterogeneity. (p. 218, original italics). He proposes that we grant Fodor that gerrymandered disjunctions are not suitable for framing laws. The crucial point to note now is that disjunctions of the realizers of functional kinds are not gerrymandered. Why? Because in order to count as realizers of a given functional property, all the disjuncts must play the causal role that defines it. This is where Papineaus [1985] argument comes in. If special science properties are multiply realizable (and so irreducible), then their realizers must be heterogeneous. But in that case, something has to explain how all the non-identical realizer properties at, say, the physical level, share the causal power constitutive of the functional properties at some special science level, say biology. (p. 219)
The problem of evolutionary selection arises.
It would be miraculous if all the different realizer properties play the same causal roles by coincidence. Whence a dilemma: either there is an explanation of the otherwise miraculous coincidence, or special science properties are not multiply realizable after all. (p.219)
Is this really an evolutionary problem? Im not sure I understand Yatess argument here. He talks about projectibility just as Loewer does, and I dont know what that is. It may be that special science properties are indeed multiply realizable, but that there is something special about whatever realization happened to develop first. The algorithm doesnt care about how it is realized (implemented) just so long as an implementation of the basis functions is available.
Now, I dont care whether RP or NRP is the right name to blazon on the banner of Truth, but I do care about making sense of things. Rather than talk about special sciences, lets talk about algorithms and their implementations.
==================== Notes ===================
[1] Loewer, Barry. 2007a. Mental Causation, or Something Near Enough. in Philosophy of Mind.
[2] Loewer, Barry. 2007b. Why is There Anything Except Physics? To appear in Synthese Special Issue on Fodor (2007).
[3] Yates, David. 2005. The Causal Argument for Physicalism. Kings College London. Doctoral Dissertation.