"This book examines the origins and extent of religious heresy in western Europe in the high Middle Ages by looking at the evidence from a regional perspective." "Part one re-visits debate concerning the origins of 'heresy' reported in c.1000. It argues that while there may have existed indigenous forms of dissent in Aquitaine, it is likely that some of the ideas identified by contemporaries as being deviant had their origins in Balkan dualism." Part two is an account of the Cathar heresy in the borderlands between the Toulousain and Aquitaine. Focusing on the families and towns of the northwestern Languedoc, previously neglected evidence relating to the rejection and reception of dualism is discussed as part of a wider examination of the political and cultural life of the county of Agen.