Prof. Sennis will present findings from his new book (ed.) Cathars in Question (Boydell and Brewer 2016) that challenges previous understandings of heresy in the Middle Ages. Using revisionist scholarship on “Catharism” as a case study, Prof. Sennis will offer a comparative perspective on issues of key interest to the study of religious groups in any period: what constituted popular belief? How was orthodoxy defined from a process of conflict and negotiation? In what ways were societies based on the suppression of dissidents? To what degree can “heresy” be seen as an invention?