The concept of "pleasure" has always bulked large in thought about human motivation and human values and standards. It seems clear to most people that pleasure and enjoyment are preeminent among the things worth having and that when someone gets pleasure out of something, he develops a desire for it. Moreover, from the time of Plato much of the discussion of the topics of motivation and value has consisted in arguments for and against the doctrines of psychological hedonism (only pleasure is desired for its own sake) and ethical hedonism (only pleasure is desirable for its own sake). One can make an intelligent judgment on these doctrines only to the extent that he has a well-worked-out view as to the nature of pleasure. Otherwise he will be unable to settle such questions as whether a putative counterexample, for instance, a desire for the welfare of one's children, is...