On Physicalism (I)
I have been reading some interesting papers on the proper characterization of physicalism. A good one is 'Physicalism' by Andrew Melnyk, from the Blackwell Guide to the Philosophy of Mind. Another one was 'Varieties of Supervenience', by Robert Stalnaker, in Philosophical Perspectives 1996.
Melnyk introduces physicalism as the thesis that all entities (objects, properties, events, etc) are either physical in a narrow sense (physical_N), that is, entities posited by physics, or physical in a broad sense (physical_B), which are appropiately related to the physical_N. Of course, the central question is how to characterize that relation between physical_N and physical_B. One important candidate is the notion of supervenience: A supervenes on B iff, any possible world that is B-identical to the actual world is A-identical.
Melnyk argues that this notion of (global) supervenience might be a necessary condition for physicalism, but not a sufficient one, because there are accounts of, say, the mental, such that mental (globally) supervenes on the physical_N but is not, intuitively, physical_B, since on that account, the mental and the physical_N are distinct entities, causally related. These accounts satisfy global supervenience, but they do not seem to be physicalist accounts.
Melnyk suggests to complement supervenience with a realization claim. A kind X is realized by the physical_N iff X is a functional kind and some physical_N entity satisfies the functional role associated with X.
Melnys argues that realization seems to be a possible explanation of supervenience.
I think this sounds plausible. However, conceivability arguments are just committed to supervenience being a necessary condition for physicalism. In other words, CA assume that physicalism entails a supervenience claim, which is compatible with a realization-based notion of physicalism (since, plausibly, realization of X by the physical_N entails supervenience of X on the physical_N).