PIETRO D'ALFONSO. – Jewish physician (Mosè Sephardi), born at Huesca (Aragon) in 1062, converted at the age of 44, died ca. 1110. A profound student of the Bible and of Arab thinkers, he was baptized by Stefano, bishop of Huesca, on 29 June 1106 and took his “surname” from Alfonso VI, king of Castile and León, who was his godfather and retained him as his physician (P. calls him his “spiritual father”).
To vindicate the biblical foundations of his conversion against the calumnies of his former coreligionists, he set forth its circumstances (in the Prologue) and its reasons in the 18 dialogues Petri cognomento Alphonso ex iudaeo christiani et Moysi iudaei (the author before his conversion): “Mosè” raises the difficulties and “Alfonso” resolves them. The work, written in an attractive style, is erudite, methodical, and of great interest for knowledge of anti-Christian conceptions (especially the first 4 dialogues) and of the formalism of the Israelites of the twelfth century; it played a considerable role in the apologetics of the period. It is praised by R. Martini (Pugio fidei, III, 3,4), Vincenzo di Beauvais (Spec. hist., XXV, 118), and Matteo Palmieri (Cronaca, a. 1068). Perhaps the anti-Christian writings of R. Jacob ben Ruben (Milbamoth 'Adhānā), 1170) and of R. Shēmōbh ben Jishāq of Tudela ('Ebben bōhen) were intended as responses to P. It was printed at Cologne (1536), and later in PL 157, 335-672. P. also composed the didactic-moral work Disciplina clericalis, consisting of a prologue and 30 fables, translated from Arab authors and incorporated into a dialogue between a dying Arab and his son; several fourteenth-century storytellers depend on II. It was published (2 vols., Paris 1824) by J. Labouderie, vicar general of Avignon, who added two ancient French vernacular versions, one in prose (fifteenth century), the other, older, in verse; P.'s text is reproduced in PL 157, 671-706.