Book excerpt: The Cathars are one of the most famous heretical movements of the late twelfth and early thirteenth centuries. They infiltrated the highest ranks of society and posed a major threat not only to the Catholic Church but also to secular authorities as well. The movement was finally smashed by the crusade and the inquisitional proceedings that followed. This new study is the first comprehensive history of the Cathars. It addresses major topics in medieval history including heresy, orthodoxy and the Crusades as well as providing a history of the social and political history of Languedoc and the rise of the Capetian dynasty. A fascinating study of the development of radical religious belief and its violent suppression.