At one point in his paper Munro uses the Shakers as an example of an ethics at odds with evolutionary biology. There are at least two ways this could be understood, one of which is plainly untenable and not what Munro has in mind, though it’s worth mentioning. If we take “doing X is natural” to mean something like “we are genetically disposed to do X” then we can probably conclude that the Shaker insistence on celibacy is unnatural. No one should conclude from this that celibacy is wrong, and fallacy of doing so is widely recognized.
I take it then that Munro’s point was more along the lines that the Shakers were guilty of a different fallacy, of insisting on and “ought” where there is no “can”, insisting in other words, on a commitment that is psychologically unrealistic because it runs so counter to our basic nature. This is not as clear cut as it might seem, though there’s something right about discounting moral theories that are simply impossible for humans to follow. What’s not clear is just how unrealistic a moral theory has to be before it’s disqualified. It should be ok that a theory demands things that are difficult but not impossible (what normative theory worth it’s salt doesn’t?). Perhaps there’s a principle here, sort of like that of parsimony, that all else being equal we should prefer a less psychologically demanding normative theory. In any case, it seems that the contribution of evolutionary biology to this discussion would be comparable to that of any other science that might inform our understanding of our natural tendencies. Once again we find that biology per se carries no normative weight. Mencius comes out looking pretty good on this score, and not just by Munro’s lights. I also heard a talk by David Wong just recently that presented a broad case for the psychological plausibility of Mencius’ understanding of moral development, and the case has also been made by the primatologist Frans de Waal as well.
In a future post, which hopefully will be coming soon, I’ll consider a third way in which we might try to find a direct normative role for biology.