Trying to understand morality involves grappling with seemingly irreconcilable conflicts between opposing theoretical positions. Originally published in 1986, this book offers a solution in terms of natural law, which involves reflections on the relevant aspects of human nature and the human condition, as well as on the special nature of prescriptive language. It also discusses several major movements in moral philosophy, both classical and contemporary and examines them in the light of a set of tests for an adequate moral theory.