Start with these three facts:
- I have good (prima facie) reason to promote my own survival.
- I believe (1).
- I know (1).
This means that the evolutionary explanation of fact (2) isn't the whole of the relevant story about why I have the belief that promoting my survival is worthwhile. We need, thus, an explanation of fact (2) that connects that belief with the normative fact (1). I doubt that naturalism can provide such a connection. Theism, on the other hand, can. For God could have deliberately created us in such a way that evolutionary processes would lead us to true belief in (1). On this theistic evolutionary story, it is no coincidence that (a) we believe proposition (1) and (b) proposition (1) is true. Thus, this story is to be preferred to a naturalistic one.
But what if the naturalist denies that (1) is true? Then she either does not believe that she has reason to promote her survival or she does. If she does believe it, then she contradicts herself—she believes something that she takes not to be true! But if she does not believe it, then for what reason does she act in her daily life as if she had reason to promote her own survival?
What I like about this argument is that it takes what seems an obvious strength of naturalistic evolution, namely its ability to handily explain facts such as (2), and turns it into a liability.