A fellow blogger recently wrote “If naturalism is true, there is no reason whatsoever to think that naturalism is true.” I would argue that if naturalism were true, we should have at least six distinct (albeit interrelated) reasons to believe that naturalism is true. Indeed, on naturalism we should reasonably expect to observe various things about the world that need not (or perhaps cannot) be true on the premise that the world was created the sort of transcendent being(s) we read about in various sacred writings :
1. Methodological naturalism (science) will work
2. Mind/body dualism will lack any empirical confirmation
3. Life itself ought to be explicable in terms of natural processes (e.g. evolution)
4. Human psychology should be explicable in similar terms (e.g. sociobiology)
5. Divine hiddenness – The existence of any particular deity ought not be obvious
6. Gratuitous suffering – Malthusian/Darwinian competition for scarce resources
Of these factors, the last two are the least secure and are limited in value to certain specific deities, namely, those that care about people and hope to have relationships with them. Deistic deities need not apply, though the gods of classical monotheism (e.g. Abrahamic, Zoroastrian, Bahá’í) may well fit the bill. The best case that I've read which puts forth these last two arguments was a book by Theodore M. Drange, the essence of which one may find condensed here.
As to the fourth argument, I'm unsure I've ever seen it made in defense of metaphysical naturalism, but it seems clear that if the predictions of sociobiology are well confirmed, such evidence should count very much against the idea that the human mind is something more than a natural adaptation used by by selfish genes in an attempt to maximize their long-term efficacy in yet another eukaryotic medium. For the sake of illustration, take an example from Richard Dawkins first book, in which he calculates the degree of relatedness between parents, siblings, cousins, etc. and predicts that human altruism should be more pronounced between more closely related individuals. Assuming this prediction has been strongly validated, it is evidence that human desires and behavior may be explained in naturalistic terms rather than by the invocation of mysterious concepts such as, say, a sin-stained soul.
The first three predictions of metaphysical naturalism are so strongly confirmed as to require no further support herein, but I'd be happy to addresses any challenges thereto in the combox. For now, I'm off to torment the kids.