A groundbreaking volume that radically refocuses our study of early modern Catholicism within a wider geographical and cultural context. The intricate relationship between the Roman Church and the Christian East has long been underestimated in shaping early modern Catholicism. Similarly, scholarship on the Inquisition has largely overlooked how it interacted with members of the Eastern branch of Christianity. Yet these groups frequently faced the scrutiny of the judges of the faith, who were, in turn, exposed to alternative disciplinary and doctrinal models that questioned Catholic certainties. This volume delves into the debates surrounding the compatibility of Eastern norms and traditions with the principles of the Counter-Reformation, focusing on Greek, Arab, and Slavic communities, as well as Armenians, Ethiopians, and Syriac Christians from the Ottoman Empire and India, among others. The essays examine topics such as the confessional surveillance of Eastern Christians in Catholic territories and the responses of Roman theologians to thorny questions posed by missionaries around the globe. Through a meticulous study of rich, untapped archival resources in a wide array of languages, this collection reveals how the interaction with Eastern Christianity exposed some of the contradictions and unresolved problems of Tridentine Catholicism, while providing the Inquisition with a set of cultural tools and interpretive lenses that would eventually be applied in the missionary and theological controversies that shook the Catholic world from the seventeenth century onwards. Chapters 1, 2, 7 and 12 are available here as Open Access under the Licence CC BY-NC-ND