This innovative approach to freedom starts from an account of what we mean by describing someone, in a psychological vein, as a free subject. Pettit develops an argument as to what it is that makes someone free in that basic sense; and then goes on to derive the implications of the approach for issues of freedom in political theory. Freedom in the subject is equated with the person's being fit to be held responsible and to be authorized as a partner in interaction. This book is unique among contemporary approaches - although it is true to the spirit of classical writers like Hobbes and Kant - in seeking a theory that applies to psychological issues of free agency and free will as well as to political issues in the theory of the free state and the free constitution. The driving thesis is that it is only by connecting up the different issues of freedom, psychological and political, that we can fully appreciate the nature of the questions involved, and the requirements for their resolution. The book does not not seek a comprehensive reach just for its own sake, but rather for the sake of the illumination it provides. A Theory of Freedom is a ground-breaking volume which will be of wide interest to scholars and students in political philosophy and political science.