Conversions often induced converts to produce literary outputs, such as autobiographies, describing the motives that made them to convert, or refutations of their former religion. Both genres are to be found among the literary outputs of the convert to Islam Samaw'al al-Maghrib? (d. 570/1175). His polemical treatise against Judaism, Ifham al-yahud, had a significant impact on the later development of the genre. Ibn Kammuna (d. 683/1284) rejected numerous objections raised in this work against Judaism in his Tanqih al-abhath, and the tract also served as a reference text for some later authors polemicizing against Judaism.Since the first critical edition of the text by Moshe Perlmann published in 1964 it is known that Samaw'al had written two versions of Ifham, the first completed in 558/1163 and the second in 562/1167. New manuscripts discoveries show that the earlier version was not replaced by the later but rather continued to circulate during the following centuries. It seems that in the East the earlier version an edition of which is presented in this volume seems to have been more widespread whereas farther West the longer version was apparently more popular.