Peter the Venerable (d. 1156), the powerful abbot of Cluny, left behind not only extensive letter collections, but also polemical treatises intended to refute contemporary challenges to Christianity. Perhaps the most important is Against the Inveterate Obduracy of the Jews (Adversus Judeorum inveteratam duritiem), written between Against the Saracens (ca. 1150) and Against the Petrobrusians (ca. 1139-41).

Against the Inveterate Obduracy of the Jews represents a turning point in medieval anti-Jewish polemics. On the one hand, the polemic's...