This useful handbook offers eighteen studies about heretical belief and practice in the Christian tradition from the second century to the dawn of modernity. It comprises two thematic sections of uneven length. Following an introduction by the editor, the first section (‘Approaches and evidence’) proposes methods for the study of premodern heresy and examines the most important genres of late ancient and medieval sources that provide evidence for reconstructing the beliefs and routines of Christian individuals and groups deemed to have been heretical. As John H. Arnold notes in his contribution, modern scholarship tends to approach heresy ‘as something constructed by orthodoxy, with the work of the historian being to take apart that construction and reveal its workings’ (p. 23). Central to this enterprise are the premodern sources that articulate the ways in which orthodox authors interrogated, combatted and vilified Christians who embraced theological positions or devotional practices that challenged their authority, including dialogue literature (chapter ii), heresiological catalogues (chapter iii), the acts of Church councils and canon law (chapter iv), and Inquisition and trial records (chapter v). These chapters are generally thorough and well researched but, perhaps owing to space restrictions, Rebecca Rist’s treatment of Church councils begins in the eleventh century and thus overlooks the transmission and influence of Greek acta in western Europe in the early Middle Ages, a topic worthy of more attention.

The second and much longer section of the book (‘Case studies’) provides state-of-the-question essays on thirteen discourses about false belief in the premodern world. Organised in roughly chronological order, these include Gnosticism (chapter vi), Manichaeism (chapter vii), Arianism (chapter viii), Pelagius (chapter ix), the Nestorian controversy (chapter x), Islam (chapter xi), Iconoclasm (chapter xii), accusations of heresy between the Eastern and Western churches (chapter xiii), Bogomils (chapter xiv), the Cathars (chapter xv), the Waldenses (chapter xvi), the Lollards (chapter xvii) and the Hussites (chapter xviii). These essays vary in their treatment and tone. For example, Robin Whelan’s chapter on Arianism and Judith Herrin’s chapter on Iconoclasm both offer exemplary overviews of their respective topics that are admirable for their clarity and thoroughness. Other chapters, like Andrew P. Roach’s contribution on the Bogomils, offer a narrower approach, in this case by examining in rich detail the single authoritative tenth-century source for this dualist belief system in the context of the religious culture of the first Bulgarian empire. At the other end of the spectrum, Jörg Feucher’s chapter on the Cathars focuses exclusively on recent historiographical controversies. With admirable clarity, he maps the battlelines drawn between revisionists like R. I. Moore and Mark G. Pegg, who deny the existence of the Cathars, and anti-revisionists like Pete Biller and John H. Arnold, who insist on the possibility of the recovery of Cathar beliefs and practices from the extant, though usually hostile, sources. For his part, Biller’s own contribution on the topic of the medieval Waldensians is couched in an informal, almost irreverent, tone at odds with the sober register of the other essays in the volume.

Few scholars will read The Cambridge companion to Christian heresy from cover to cover, so the chapter that draws their eye to the book will influence their impression of its utility. But, overall, this collection succeeds in providing helpful orientation and bibliographical guidance to those interested in premodern heretical groups, the sources for their history, the difficulty of reconstructing the beliefs and practices associated with them, and the debates engendered by this challenging enterprise.