This text contains 15 essays which together show the development of one of the more important contemporary theories of the nature, grounds and practical implications of rights. The author provides a critical perspective both on his own theory and on alternative theories from which he borrows, or that he rejects. These essays identify the problems any adequate theory of rights must solve, describe the more plausible solutions and weigh the merits of each. They should be of interest to any reader concerned with legal theory, moral philosophy or any branch of applied ethics or social policy.