This post is part of my series on physicalism.
When I started reading about physicalism I thought, "This is going to be a no-brainer - a piece of cake - a clear shot at an open goal - a badly mixed metaphor." After reading these two books, I am impressed with the difficulty of the task. I think I understand a little better, too, how people like Trent can be so skeptical of the whole operation.
The issue with defining "physics", so that we can know what to reduce everything down to, seems almost a red herring. After all, if we could show that mental processes reduce down to events at the neural level, I don't think it would matter all that much (to philosophy) which definition of "physical" was taken to underlie the neural level. The biggest problem here is one that is glossed over briefly by Poland and sidestepped entirely by Melnyk: namely, the problematic nature of the ontology of quantum mechanics. If the wave function cannot be consistently interpreted as an actual, physical object (as I would argue), then it can't be the foundation for ontology for everything else. Poland waves such worries aside and says these things are for the physicists to worry about: whatever they come up with as the basic ontological entities are fine with him. But what if those basic entities can only be defined in term of large-scale, macroscopic quantities and measurements, as quantum mechanics seems to do? Then physicalism might justifiably be accused of circularity.
The more important point, it seems to me, is the issue of "realization." These two authors agree that supervenience is too weak, and identity theses are too strong. If realization gives a coherent account of how higher-level things are related to (reducible to) lower-level things, then something of real importance has been achieved. And this achievement is independent of the issue of what sort of physics is at the base of it all.
Finally, is realization physicalism (or something like it) is actually true? It is not so clear what, exactly would count as evidence in favor of, or against, physicalism. Melnyk spends two chapters considering the question and looking at the evidence, such as it is. He points out that some phenomena that might have turned out to be clear evidence against physicalism - psychokinesis, for example - have not panned out so well. On the other hand, more positively, every sort of mental activity seems to be associated with some sort of brain activity (e.g. as revealed in functional MRI investigations). He notes, too, that as recently as 1925 a prominent philosopher, C. D. Broad, could doubt that chemical phenomena were reducible to underlying physical laws, whereas now it is clear that the rules of quantum mechanics explain much of chemistry.
In short, physicalism has suffered no decisive defeat and has scored many major victories. This alone doesn't settle the matter, of course., and dualists and theists will continue to assail the physicalist position.
I still think that physicalism is clearly the most reasonable view - simply because of the complete lack of evidence for anything that is not physically realized. In this it is just like atheism: show me the evidence for your god, and perhaps I'll believe in him. (Or her.) (Or it.)