“We’re all in favor of moral rules that prevent others from doing things that harm our own interests. Just look at the Seven Deadly Sins, a list of all those things we don’t want other people to do, though we might well have an interest in doing them all ourselves. (Symmetrically, “virtues” are traits you want other people to possess—altruism, modesty, chastity —even if you yourself are better off avoiding them.)”