This volume is a collection of thirteen seminal essays on ethics, free will, and the philosophy of mind. The essays deal with such central topics as freedom of the will, moral responsibility, the concept of a person, the structure of the will, the nature of action, the constitution of the self, and the theory of personal ideals. By focusing on the distinctive nature of human freedom, Professor Frankfurt is able to explore fundamental problems of what it is to be a person and of what one should care about in life.