This book examines key twentieth-century philosophers, theologians, and social scientists who began their careers with commitments to the political left only later to reappraise or reject them. Their reevaluation of their own previous positions reveals not only the change in their own thought but also the societal changes in the culture, economics, and politics to which they were reacting. By exploring the evolution of the political thought of these philosophers, this book draws connections among these thinkers and schools and discovers the general trajectory of twentieth-century political thinking in the West.