This introduction presents an overview of key concepts discussed in the subsequent chapters of this book. The book examines preaching about the Jews in Late Roman and Visigothic Iberia against a background of fear of Jewish contamination to which, the Church hierarchy maintained, Christian communities were exposed. It looks at the portrayal of Jews in late fifteenth-and early sixteenth-century vernacular sermons from Denmark, a country that at the time was without any resident Jewish community. The book investigates the largely unpublished anti-Jewish sermons of the Franciscan friar John of Capistrano. It explores the role of animals in the didactic and exhortatory writings of the Ḥasidei Ashkenaz. The book traces the stereotype of Jews as fences from the time of its creation by Peter the Venerable in the first half of the twelfth century. It shows the longevity of anti-Jewish preaching-from late Antiquity to the early modern period-and its ubiquity in all parts of Western Europe.