In Macbeath’s treatment of ethics and the moral life, he defends the assumption that the main structure of the moral life, the nature of the moral idea and the grounds of moral obligation are in principle the same everywhere and for all people; and that, therefore, only a theory which will account for the moral judgments of all persons can be regarded as a satisfactory ethical theory. He contextualizes his subject through the study of the moralities of contemporary primitive peoples—Trobriand Islanders, a Bantu tribe, Australian aborigines, and Crow Indians. The author draws on such groups partly in order to show the wide range of facts for which ethical theory has to account, and partly because the contrasts between the ways of life and the moral judgments of different peoples are more obvious in the simpler conditions of primitive life. In the end, Macbeath concedes that though the conclusions he arrives at about the moral life do not seem to him to derive their justification or authority from any metaphysical or theological system, they are not without metaphysical implications.