Noticing what Steno did here, that animal rights activist philosopher Peter Singer is moving toward the idea that morality has an objective basis, anti-ID Catholic philosopher Ed Feser responds. Noting that Singer is looking for an “intuitive” basis for morality, he writes,
Moral intuitions track objective moral truth in only a very rough, general, and mutable way. Practically they are useful – that is why nature put them into us – and they might provide a useful heuristic when philosophically investigating this or that specific moral question. But intuition does not ground moral truth, it is not an infallible guide to moral truth, and it should never form the basis of a philosophical argument for a controversial moral position.
But that won’t work. If “nature” put the intuitions into us, they could be any intuitions at all, unrelated to morality or even survival.
The Darwinist will, of course, want to say that our intuitions help us survive and pass on our genes. But the fact is, many life forms, corporately and individually, fail to survive by their intuitions. Real rules must be enforced from outside the conflict. So “objective”, as it happens, must mean outside and beyond nature. Then nature does not in fact do any putting in, except as directed. But presumably, the fiction that nature does something must be maintained; otherwise, people might think it was design.
Note: Here’s a look at the first step toward Singer’s change of mind: Caring for his aged mother.