This is an intriguing and rewarding book, combining personal reflections with an analysis of strategic problems and some specific policy prescriptions. The book reveals Freeman Dyson to be a man of strong humane instincts, aware of the political and technical complexity of our nuclear dilemmas, and searching for solutions at the most fundamental level. Understanding the intellectual universes of the military establishment and weapons scientists, as well as that of the peace activists, he seeks to explain their differing assumptions to each other. The most important sections, however, deal with strategic analysis and in particular with anti-ballistic missile defenses. Dyson rejects the concept of Assured Destruction, arguing that it is not shared by the Soviet Union and that it is immoral, and suicidal in its vulnerability to accident or human folly. He recommends moving toward a defense-dominated world and proposes the adoption of a non-nuclear ground-based ABM. The fly in the ointment is that this presupposes the severe curtailment of offensive forces, and Dyson's argument fails to acknowledge the difficulty of this major step. Nor does he deal adequately with space-based defense, in what is otherwise a truly admirable book.