In Defining Heresy, Irene Bueno investigates the theories and practices of anti-heretical repression in the first half of the fourteenth century, focusing on the figure of Jacques Fournier/Benedict XII (c.1284-1342). Throughout his career as a bishop-inquisitor in Languedoc, theologian, and, eventually, pope at Avignon, Fournier made a multi-faceted contribution to the fight against religious dissent. Making use of judicial, theological, and diplomatic sources, the book sheds light on the multiplicity of methods, discourses, and textual practices mobilized to define the bounds of heresy at the end of the Middle Ages. The integration of these commonly unrelated areas of evidence reveals the intellectual and political pressures that inflected the repression of heretics and dissidents in the peculiar context of the Avignon papacy.