Where does the evolutionary argument for naturalism work?

I’ve never been moved by Plantinga’s evolutionary argument against naturalism in general, but I’ve also always found it plausible that naturalism and evolution undercuts cognitive reliability in certain areas, such as metaphysics. It seems, on the other hand, really plausible that we would get cognitive reliability for empirical things (largely because of the fact that naturalism makes causal theories of content very likely).

One might go on to conjecture that Plantinga’s argument works everywhere outside of empirical areas. I thought so until I realized that there is a significant area of normativity where the argument doesn’t work: prudential value judgments. This is because that life and reproduction is good for living things, and many other goods, noncoincidentally, contribute to life and reproduction. But at the same time, we are evolutionarily selected for successful promotion of life and reproduction. A being that believed that life is bad would be unlikely to promote its own survival, and hence unlikely to pass on its genes.

Plantinga’s standard answer to similar objections in the empirical arena is that behavior does not come just from beliefs, but from a combination of belief and desire. But this response is rather implausible in the prudential rationality case. It is extremely plausible that there is a conceptual link between a mental state representing something as good for one and having a desire for that thing. If there were no correlation between a mental state S respecting a thing and having a desire for that thing, that mental state just is not a belief that the thing is good for one.

A constraint on metaethics

Suppose that we lived lives like ours in a world (possible or not) whose metaphysics included nothing like moral duties except that there was a loving God and he issued commands. If in that world we used the phrase “morally wrong”, that phrase would refer to the property of being forbidden by God.

Or suppose that we lived lives like ours in a world (possible or not) whose metaphysics included nothing like moral duties except that we had Aristotelian forms and they specified what the will should will, the phrase “morally wrong” would refer to the property of being contrary to what our form says the will should will.

But suppose now we lived in a world where there was nothing like moral duties, no God, no forms, but buried underground and unseen by humans there was a stone tablet that arose from a random volcanic process millions of years ago. On these tablets by chance there were markings that looked just like French sentences, and when interpreted as French sentences, they stated imperatives, like the Golden Rule, that that fit very well with our intuitions about what are the core moral duties. I doubt that the phrase “morally wrong” would refer to the property of being contrary to what the stone tablet would enjoin if it were interpreted as French. (I am careful in my wording, because strictly speaking the stone tablet, being the product of random processes, does not contain any sentences—it only contains markings that look like sentences of French.)

Suppose my intuition is right. What is the difference between the third case and the first two? Here is a hypothesis. In the divine command world, presumably our beliefs about what we call “morally wrong” have some sort of a connection to the commands of that God. In the Aristotelian world, our beliefs about the “morally wrong” presumably come in some way from the Aristotelian forms. But in the stone tablet world, the “morally wrong” beliefs have no connection to the stone tablets, except that the stone tablets happen to fit them.

This suggests an important constraint on metaethics: our beliefs about the morally wrong had better have a real connection—perhaps even a real causal connection—with their grounds. If this constraint is right, then evolutionary debunking arguments against morality cut more deeply than is recognized: if the arguments correctly show that our “moral concepts” lack a relevant connection with any grounds, then our “moral beliefs” not are not knowledge, but they are in fact just nonsense.

Of course, I want to turn this around: given that our moral beliefs are not mere nonsense, it follows that they have a real connection with grounds, and this undercuts the idea that we are mere products of completely unguided evolution.