Abstract

I formulate and defend a realist theory of the truth of moral judgements according to which moral properties are synthetically but necessarily determined by natural properties of people, actions, or states of affairs. This view can be found in Moore's later ethical writings. The view reconciles two apparently conflicting intuitions: Moral properties supervene upon natural properties, but judgements about moral properties are generally not entailed by any judgements about natural properties. The view is realist in the sense that moral judgements possess a truth-value independently of our means of knowing it. They are true or false in virture of a reality existing independently of us. ;One promising way of understanding this synthetic, necessary connection between moral and natural properties is in terms of the Kripke-Putnam account of natural kinds: Moral properties are type-identical with configurations of natural properties. But this turns out to be unsatisfactory. Another promising way of understanding this connection is on analogy with the connection between the mental and physical. I reject a token-identity theory of the moral and natural, but the analogy itself is helpful in understanding the relationship between the moral and natural. It offers a model for that relationship. ;I distinguish two senses in which supervenience could be understood in morality--ascriptive and descriptive--and argue that ascriptive supervenience depends on descriptive. A realist must defend descriptive supervenience. Moral properties decriptively supervene upon natural properties because moral differences must be explicable and justifiable in terms of natural differences. ;I construct an epistemology for moral properties in which natural properties are criteria, in Wittgenstein's sense, of moral properties. This conforms with the metaphysics of moral properties, and can be reconciled with the phenomenon of moral conflict. Finally, a careful formulation of moral realism is defended against Dummett's objections to realism generally. The moral realist cannot be forced to hold that there are moral truths that humans could not, even in principle, come to know. Yet this is what seems objectionable about realism in other realms. We can know all moral truths in principle, though perhaps not in practice