A reductio ad absurdum
…of evolutionary psychology as a delegitimizing genealogy of morals (but not really a reductio ad absurdum; see below).
The argument itself, in case you haven’t hung out around enough moral skeptics lately, goes something like this:
There’s a perfectly persuasive evolutionary account of our moral intuitions. They’re a survival advantage, and were thus selected for. Therefore our moral intuitions don’t tell us that morality is “real,” in the way that an “objective morality theorist” would like it do be, just that (at one time) it was advantageous.
The provocative ones point this out about love and sex, too. Now, this argument is slyer than it’s sometimes given credit for being. Nietzsche’s original genealogy was said to suffer from the genetic fallacy. So would this argument (rather amusingly, given both the word “genealogy” and the word for the study of biological heredity), if it were taken to be a proof of the falsehood of “objective morality.”
That said, it isn’t, and I don’t think Nietzsche’s genealogy was either. The point wasn’t to prove morality didn’t exist, the aim was more modest: to invite skepticism regarding the moral tales we tell ourselves, by showing us how they might be (not how they necessarily are) contingent truths.
This is all well and good (or maybe not good, since we’ve cast doubt on that concept) and more persuasive than genealogy as purported proof. I mean to fuel the fire a bit in the other direction though. This isn’t a proof-positive of the irrelevance of the skeptical argument above, but is does show that the argument has some interesting conclusions:
There’s a perfectly persuasive evolutionary account of human reason (geeks, please read “reason” as “approximately Bayesian subconscious inductive heuristics”). Therefore, human reason doesn’t tell us truth, it just causes certain behavior that at one time was advantageous for survival.
This is an issue in all psych. On some level, it has to be a bit “naïve realist” about itself. Otherwise, you’ve got cognitive bias all the way down. You can’t call a bias a bias unless you possess some more accurate model of reality that you can use to show that the “biased” perspective is distorted. At the same time, the accuracy and persuasiveness of of evo-psych depends upon very same human reason that it can be used to delegitimize/throw into question.
The sensible response here, it seems to me, is not to reject reason but to reject the claim that evolutionary provenance throws its efficacy as a means of discovering truth wholly into question (though we may graciously admit that it does force us to be more aware of our own biases—an admission that, as argued above, ultimately affirms the power of reason).
What bearing does this have on moral philosophy? Only that our confidence in certain other evolved judgment standards is not undermined by their status as products of evolution. This doesn’t mean our confidence in our moral standards shouldn’t be an exception to this. Like the weaker and more persuasive version of the genealogical argument it goes up against, it merely seeks to show why we need not accept a philosophical conclusion. Whether we should not is another (rather normative) story.