For Thomas Aquinas the peculiar mark of the human agent is that he consciously directs himself to the goods he recognizes as fulfilling of him. Ralph McInerny presents Thomas's moral philosophy as flowing from this conception of man as a rational agent. Beginning with the human person choosing and making decisions in the changing circum- stances of life, he brings out the notion of the human good or human end implicit in all action and decision and investigates the development of this notion in Aristotle and Thomas. The permanent truths about the human good which can be formulated when it is so considered are for Thomas the first principles of natural law. In a discussion which includes a critical assessment of some recent interpretations of Thomas's theory of natural law, Professor McInerny shows that the model of moral decision involved in natural law - the application of general precepts to the particular situations of life-complements the analysis in terms of "human end." The chapters which follow carry the analysis of the human good further into discussion of the structure of the human act, the constituents of good and bad action, moral character as the source of moral actions, the roles of prudence and conscience, Thomas's understanding of the relation between morality and religi While the exposition relies for the most part on texts of Thom Aquinas, an awareness of contemporary issues and approaches is pr ent throughout.