What is ethics? Where does it come from? Can we really hope to find any rational way of deciding how we ought to live? If we can, what would it be like, and how are we going to know when we have found it? To capture the essentials of what we know about the origins and nature of ethics, Peter Singer has drawn on anthropology, evolution, game theory, and works of fiction, in addition to the classic moral philosophy of such thinkers as Nietzsche, Kant,...