I was reading the NPDR reviewof a recent book on the philosophy of David Armstrong. I found this review very interesting as I have been very influenced by David Armstrong myself (and have even had the privilege of auditing his course on truthmakers at the Graduate Center) though I can’t say I agree with all of his views. At anyrate, in light of all of the zombie stuff lately this got me to thinking.
Naturalismis a metaphysical thesis that claims that everything that exists does so entirely in one single space-time system. Both idealists and materialists/physicalists can be naturalists in this sense. This is to be distinguished from empiricism which is the epistemological thesis that claims that the only way to acquire knowledge is the empirical a posterori way used by science. Armstrong’s main argument for naturalism relies on what he calls the Eleatic principle. This principle says that we ought NOT to posit the existence of entities that have no causal powers. So, if empiricism is correct then the Eleatic principle offers strong support for naturalism and from naturalism to materialism/physicalism.
Why should we adopt empiricism? The best argument I have seen is Devitt’s abduction. He argues that when we have two competing theoretical explanations we should opt for the one that is better understood. I think there are other, related reasons for adopting empiricism. In the first case we have never had to appeal to non-natural entities in any succesful explanation. Each time we have appealed to some non-natural entity we have eventually discovered a plausible candidate for a natural explanation. I have also argued that if anything like evolution turns out to be true then we cannot appeal to intuition as evidence for rationalism (and against empiricism). This is because, given that the our experience of the world has been regular and uniform up until now, we would expect that there would be certain truths which seem to be self-evident but are really just the product of a long process of natural selection in response to a stable environment. If this were the case we would have the very same intuitions that the rationalist appeals to and so the rationalist must have another argument. But none that I know of have been given.
The Eleatic principle also is wielded as an argument from naturalism to materialism. If a non-material entity has no causal powers then according to empiricism we cannot know about it and so would never have any reason to posit its existence. If it does have causal efficacy then it is of a type that is completely mysterious and unlike anything that we have hitherto encountered. So materialism is itself an empirical hypothesis.
So, if one were to ask ‘but why is it matter rather than something else?’ The answer would be ‘because we discovered that waht it is’. If one wanted more than this, and insisted on asking ‘but what is the reason that it was that way to be discovered?’ The answer would be that it happens to be the case that the actual world is one where there is causation and you need material for that.