This collection reveals the development of Popper's political and philosophical thought during and after the Second World War, from his early socialism through to the radical humanitarianism of The Open Society. These papers, many of which are available here for the first time, demonstrate the clarity and pertinence of Popper's thinking on such topics as religion, history, Plato and Aristotle, while revealing a lifetime of unwavering political commitment. The volume also includes fascinating correspondences with Rudolf Carnap, Friedrich Hayek and Isaiah Berlin, as well as important reflections on the Cold War, the treatment of Germany after the Second World War, the Vietnam War, nuclear weapons, and the use and misuse of television.