This volume examines the influence of R. I. Moore and the nature of heresy and its repression in the Middle Ages. The volume considers the vexing question of the origins of medieval heresy and the possible influence of Bogomil missionaries. Geographic areas not usually examined for the growth of heresy are examined, and a new understanding of the violence of the Albigensian Crusade is offered. The blurred boundary between heresy and orthodoxy and the nature of heresy and popular religion are also discussed. The final chapters consider the formation of the persecuting society and Moore’s reflection on scholarship of the late 20th century. The volume offers new insights into the nature of heresy and society in the Middle Ages.