Dr Georg Eder was an extraordinary figure who rose from humble origins to hold a number of high positions at Vienna University and the city's Habsburg court between 1552 and 1584. His increasingly uncompromising Catholicism eventually placed him at odds, however, with many influential figures around him, not least the confessionally moderate Habsburg Emperor, Maximillian II. Pivoting around a dramatic incident in 1573, when Eder's ferocious anti-Lutheran polemic, the Evangelical Inquisition, fell under sharp Imperial condemnation, this book investigates three key aspects of his career. It examines Eder's position as a Catholic in the predominantly Protestant Vienna of his day; the public expression of Eder's Catholicism and the strong Jesuit influence on the same; and Eder's rescue and subsequent survival as a lay advocate of Catholic reform, largely through the alternative protection of the Habsburgs' rivals, the Wittelsbach Dukes of Bavaria. Based on a wide variety of printed and manuscript material, this study contributes to existing historiography by reconstructing the career of one of late sixteenth-century Vienna's most prominent figures. In a broader sense it also adds significantly to the wider canon of Reformation history by re-examining the nature and extent of Catholicism at the Viennese court in the latter half of the sixteenth century. It concludes by emphasising the importance of influential laity such as Eder in advancing the cause of Catholic reform, and challenges the prevalent portrayal of the sixteenth-century Catholic laity as an anonymous and largely passive group who merely responded to the ministries of others.