Petrus Alfonsi's Dialogue Against the Jews (ca. 1109) breaks new ground in the history of Christian anti-Jewish polemics. As a recent convert from Judaism, Alfonsi introduced an intimate knowledge of Jewish literature and contemporary practice absent from earlier Christian sources. This knowledge enabled him to attack for the first time the Talmud (or, more broadly, post-biblical Jewish literature) as a source of Jewish error, with arguments...