This thesis examines the definition of religious orthodoxy promulgated by Peter the Venerable in the Adversus Iudaeos, a twelfth-century anti-Judaic polemic. Scholars have thus far categorized this polemic as a typical and traditional guidebook designed to aid monks in the refutation of Jews using scripture, logical argumentation, and an engagement with post-biblical Jewish holy text (and in this case, the Talmud). Despite this categorization, scholars have neglected to discuss the role of emotions in categorizing Judaism. I argue that Peter uses the emotional rhetoric of disgust to alter the traditional polemical purpose ascribed to it. When Peter compares Jews to “useless vomit”, he suggests that a Jewish way of thinking is filthy and worthy of disgust. These acts allow Peter the ability to unify and define his own version of Christian thought, and contrast it with the framework of thinking adopted by his rival monastic group, the Cistercians.