For a millennium heresy has been central to ‘the making of European culture’. Indeed, claims for its centrality could be pushed back to well before the year 1000, to the Nicene Council and even earlier debates around the nature of Christian orthodoxy. But the formative battles of the Roman period were long past by the eleventh century when western Europe began its economic, demographic, and intellectual ‘leap’ forward toward the modern world. From the Gregorian reforms to the Protestant Reformation and beyond, heresies and heretics helped to shape the religious, political, and institutional structures that medieval Europe would bequeath to the modern West. Within this sweeping history, the late medieval period, traditionally understood as the fourteenth and fifteenth centuries, presents a particularly diverse array of heterodox movements and modes of thought. Yet despite this richness, or perhaps because of it, some of the most intriguing heresies and heretics from this era of ‘paradox, tension, and unpredictability’ have been undervalued in wider studies, treated either as epilogues to the better-studied twelfth and thirteenth centuries or as preludes to the epoch-making religious revolutions of the sixteenth.

This introduction first addresses the historiographic landscape of medieval heresy, focusing in particular on periodization and its consequences. Then, as befitting a collection honoring the pioneering work of Robert E. Lerner, it outlines the elements of a ‘Lernerian’ approach to late medieval heresy and suggests ways in which this approach informs the new perspectives presented here.

The Historiographic Landscape

The work of the German historian Herbert Grundmann (1902–70) has profoundly influenced scholars of medieval religious history, including – as Richard Kieckhefer's preface notes – Robert Lerner. For the field as a whole, Grundmann's most influential work was undoubtedly his brilliant 1935 study of Religiöse Bewegungen im Mittelalter, which analyzed ways in which groups that cohered around spiritual, intellectual, and cultural ideals shared by broad swathes of European society could still end up forced into dissent or at least labeled as dissidents. In this analysis, a figure such as Valdes of Lyon partook in the apostolic impulses that animated many twelfth-century figures, but when his refusal to abandon lay preaching led to condemnation, he and his followers were labeled as heretics, and many ultimately came to understand themselves as opponents of the organized Church.