All or virtually all moral philosophers agree that moral properties supervene on natural properties; that is, two actions or situations cannot differ in their moral properties unless there are differences in their natural properties that account for the moral difference between them. Virtually all moral philosophers also believe that supervenience is a conceptual or logical feature of moral discourse and judgments. While accepting that supervenience is a fundamental feature of morality, this essay contends that it is a basic substantive moral (...) constraint rather than a purely conceptual or logical feature. (shrink)