Science and Ethics, often seem to clash. But this seems needless. Our ethical intuitions survive scientific criticism of the theologies in which they are often embedded, suggesting, correctly in my view, that these intuitions are independent of theologies, and derive from other sources. Ethical realists, even of a theological variety, accept this and suggest that our moral intuitions are intuitions of facts of the universe. But here science returns to the fray, and claims that they are facts of the universe only in the sense that they are intuitions of probable self-interest, and that our morals are evolved responses assisting in the gathering of resources and the securing of reproduction. In other words that they are an adaptation, an improbable state of matter in relation to the conditions for survival and reproduction and therefore conducive to survival and reproduction.
From this perspective it is reasonable to ask whether an ethical realist deserves the name. Such people say that they believe that our ethical intuitions of right and wrong represent facts of the universe; and they claim that these facts are more than parochial in character, that they transcend local circumstances and are true universally (that rape is wrong on Andromeda, for example). But they also claim, I think, that wrong and right are absolutely so, not merely local to the universe, and thus that they transcend the universe itself. But what is this claim about? Something wrapped around the universe, it seems. Which is impossible, except in a transcendentalist system.
Thus, I wonder if the moral sceptic, who thinks that moral intuitions are only pragmatic intuitions of probable self-interest, are actually better entitled to the term "realist". Those usually describing themselves as moral realists are more accurately called fantasists, since they claim that moral injunctions are absolutely true in a sense that requires the positing of a universe other than but including the one that we know, and for which there is no evidence. And they are worse than this since it is obvious that such people are only seeking to find external sanction for their own parochial realism.
No wonder, then, that this self-knowledge is unpopular, and indeed much resisted and with extravagant gestures of distaste and horror. The strength of that reaction suggests that something important is at stake, namely that awareness of the origins of moral intuitions makes them less effective as adaptations. Morality begins to break down without the external sanction of an inferred transcendent.
In that sense it seems that self-interest and science are indeed in conflict. Whatever the sages say, nosce teipsum is only a dubiously profitable maxim; self-interest and self-knowledge are incompatible.