It is hard to see the import of a metaphysical argument that has no epistemological implications. If dualism about body and mind is correct an interaction problem will have to be dealt with. By the same token if materialism is to be taken seriously it will have to provide a naturalized account of causal explanation. I take this to mean that to espouse materialism is to commit oneself to the view that a “closed” physical explanation, that is an explanation that refers only to physical causes, is possible. Many materialists understand this to mean that there can only be one “existential question,” if an existential question is one that might not have an answer: “Why is there something rather than nothing?” The idea is that there must be absolutely nothing inherently organized about the something that exists, because materialism is the bare claim that only matter exists and must accomplish everything starting from that sole axiom. Remember, too, that early modern materialism was closely linked with empiricism, forged in opposition to the classical tradition of Neo-Platonism, Christianity and rationalist philosophy and programmatically hostile to metaphysics.
Consider, for example, the argument traditionally called “the teleological proof for the existence of God” or more recently “the intelligent design argument.” Put in currently popular terms, the argument is that the complex design of the natural universe is evidence for an intelligent designer. In this context there is a significant difference between this sort of view and double-aspect theories that see mind and matter as one ontological being, under two kinds of description. (In addition to Spinoza many Hindi and Buddhist philosophers develop versions of double-aspect theory.) In so far as the design argument is an argument meant to demonstrate the existence of another being, the intelligent agent nominally responsible for the design of nature, the argument fails. The design argument starts by asserting that any finely-organized entity must have some sort of explanation. In the case of the natural world, an evidently finely-organized entity, the explanation offered is that there exists an intelligent designer. But the advocate of the intelligent design argument, in so far as he or she takes the argument to show that an intelligent designer ontologically distinct from the natural world exists, now looks committed to the need for an explanation of this finely-organized entity in turn.
To read this back into theory of mind, a materialist theory of mind has to get to mind from no-mind. The intelligent design argument fails because it is intelligence itself (in Platonic terms, the intelligibility of the universe) that we are trying to explain, and pushing the problem back a step is a failure to explain, just as saying that representations are interpreted in your head fails to explain how you, an actual person out in the world, actually interprets anything.
However, it may be that some materialists have over-reacted to the danger posed by the slippery slope that supposedly leads from recognizing that the physical universe may have some innate organization to…what? Say, full-blown Roman Catholicism? Perhaps it is simply a matter of two existential questions, not one. In addition to “Why is there something rather than nothing?” maybe “Why is the something that there is organized such that complex physical systems with formal properties arise?” To come to accept that the universe is a formally organized place can be an entirely secular resolution, after all. Materialist biologists arguing against creationism in the public schools don’t want to work themselves into an even weirder position than that of their religiously-motivated, intelligent design-espousing opponents.
The question then becomes, does accepting that there are two existential questions, not one, entail conceding that materialism is false? I think that in a way it does. If it makes sense to say that formal organization a) exists (“obtains”: I take the Aristotelean view that formal organization, if it is real, is a feature of the physical universe) and b) is a further, contingent fact (that is, there could have been a physical universe that was not formally organized to any degree) then materialism in its most orthodox version is false. I will go so far as to say that this appears to me to be the most plausible resolution to the problem of rationality, and that I do not think that it would be the end of the world if materialism were modified in this way. It is often pointed out that contemporary physics’ picture of “matter/energy” is now so strange that the concept of “materialism” probably can’t do much reliable reductive work anyway. And it is striking that physics has become more and more mathematical as the modern movement of physics has progressed over the passed one hundred years or so.
I think, though, that I can have my resolution to the problem of rationality without settling the cosmological question about the existence (or lack thereof) of innate universal order. The orthodox materialist might be able to explain how complex, self-replicating forms emerged from random, chaotic interactions, such that there is no need for “innate order.” Or materialism may fail to do this. It is enough for my thesis if formal properties are ubiquitous in worlds where rational beings evolve. How those worlds got that way is irrelevant to the point, which is that rationality is (just) another formal property and, although rational beings may be breathtaking examples of finely-formed entities, they are not therefore ontologically distinct from the rest of the physical universe.