Why do people have the morals they have? Despite superficial appearances, this is many questions, to which I have not enough answers. I wish to address only the general structure of the ordinary person's learning of morals. I will not address the moral theorist's program of justifying morality or a particular moral theory. Rather, I will focus only on the plausible nature of common moral reasoning. In rough outline, that reasoning must be quite similar to practical reasoning for other matters. It will turn on the moral knowledge available to the reasoner. That knowledge must have been gained in ways similar to the learning of any other knowledge.

A common move in much of contemporary moral theory and criticism is to test the theory under consideration against “our” moral beliefs. If the theory does not match the beliefs, intuitions, or so-called common sense, the theory is supposed to fail. In The Methods of Ethics Henry Sidgwick makes a nearly opposite move in his account of the method of utilitarianism. He supposes that common-sense morality has a utilitarian basis (ME, 423–59). Sidgwick's is a complicated sociological and psychological claim that neither he nor many others who have made it have backed with much compelling argument. I wish to test this claim from what might be called an economic theory of our knowledge about anything, including morals.