Petrus Alfonsi’s anti-Islamic polemic was medieval Europe’s most influential source on Islam.

Evidence

The most widely read and influential of these texts was the anti-Islamic chapter of Petrus Alfonsi’s Dialogues against the Jews. Alfonsi composed them in 1110 and subsequently immigrated to England and then to France; from there, his Dialogues circulated among monastic readers interested in Old Testament exegesis, Judaism, and Islam. Sixty-three extant manuscripts of the Dialogues (along with another sixteen manuscripts containing adaptations of the text) testify to its popularity. Vincent de Beauvais included an abbreviated version of the text in his Speculum historiale (c. 1250), which survives in more than two hundred medieval manuscripts. Several scribes recopied only the anti-Islamic chapter, and the Dominican Humbert of Romans, in his Tract on the Preaching of the Crusade, recommends it alongside the Latin translation of the Koran as essential reading for understanding the religion of the adversary. Dozens of medieval writers on Islam based their descriptions of Muhammad’s life, of Muslim law, and of the pilgrimage rites at Mecca on Alfonsi’s Dialogues. — John V. Tolan, Saracens, 831

Categorization

• XREF: Establishes the actual textual vehicle by which the medieval image of Muhammad as false prophet proliferated — grounding genealogical claims that anti-Islamic tropes in Anidjar/Aziz/Razack trace to a specific twelfth-century polemical tradition.
• SEED: Angle: how a single 1110 text by a converted Spanish Jew became the default medieval European reference on Islam, more influential than the actual Qur’an translation.