This book is the fruit of well over thirty years' reflection on moral philj osophy. A complete appreciation of it requires reference to The Language of Morals (Oxford University Press, 1952) (LM), Freedom and Reason (Oxford University Press, 1962) (FR) and many of Hare's extensive shorter writings. To some, it will appear to represent a radical, if gradual, reversal of his early views. His early position was thought by some to be one similar, in certain respects, to that of certain existentialist thinkers: that the most fundamental moral attitudes must be the outcome of sheer choice, or commitment. Whereas in the latest book Hare argues that to think fully rationally about moral questions requires us to be Utilitarians (unless we are amoralists, as we shall see below).