This is the first comprehensive account in English of the most feared and the most mysterious of medieval heretics. A crusade was launched to uproot them in the south of France, the Inquisition was developed to suppress them, and St Dominic founded his friars to preach against them. Their history and that of the medieval Church are inextricably mingled.This book puts the Cathars back into the context of medieval Catholicism. It studies the rise and fall of the heresy from twelfth-century Rhineland to fifteenth-century Bosnia and the Church’s counteraction, peaceful and violent.Some argue that our knowledge of the Cathars is fatally distorted by prejudice; in fact, the author shows, we can now acquire an understanding of their beliefs and internal disputes, and the reasons why they once made so powerful an appeal. Using and assessing a rich volume of international research, the author re-examines the problems of the Cathars’ origins, the heroism of their leading class, and the balance between inner decline and external pressure in accounting for their disappearance. In this exposition, Italian Cathars are restored to their rightful place, a chapter is devoted to the puzzle of the Bosnian church, and perspective is given to Le Roy Ladurie’s brilliant but wayward Montaillou. A final survey assesses the legacy of a heresy which still exerts a strange fascination.