The seeds of heresy are contained in Christianity itself, which began as a religion of dissent. In the Middle Ages the Church was the main focus of intellectual activity, and its spiritual leaders themselves often questioned the practices and beliefs which heretics openly challenged.<BR>The documents analysed in this volume trace the development of popular heresy from its beginnings. Four main themes are presented: the first manifestations of popular dissent in the eleventh century; the emergence of evangelical anticlericalism in the twelfth century; the infiltration of western heterodoxy in the mid-1100s; and the establishment and early organization of Cathar Churches in southern France and northern Italy which ultimately led to the inquisition.