PETRUS ALFONSI (Aldefonsi ; b. 1062), Spanish Converso, physician, polemicist, and author, possibly born in Huesca. Known as Mosé or Moisés Sefardi before his conversion at the age of 44, he assumed the new name of Petrus Alfonsi (Aldefonsi) because his conversion took place on St. Peter's Day and his baptismal patron was King Alfonso i of Aragon. He spent the second half of his life in England, where he was physician to King Henry i. Petrus introduced the Oriental apologue to Western Europe through his Disciplina Clericalis, a collection of some 34 stories belonging to the traditional literature of the Orient (translated into English under the title The Scholar's Guide). He was also the author of a polemical treatise, Dialogi… in quibus judaeorum opiniones… confutanur (Bibliotheca Patrum, 22 (1677), 172ff.), which he wrote to defend his conversion.
These dialogues, cast in the mold of classic apologetics, take place between a Jew and a Christian, named respectively Moses and Peter, the two figurations of the author before and after his baptism. The work, divided into 12 chapters, begins with an attempt to prove that the Jews were only partially observing the Law of Moses. The author also touches upon Islam, to demonstrate its falsehoods. From chapter 6 on, he explores the concepts of the Trinity, the Immaculate Conception, the Incarnation, and the supposed fulfillment of prophecies with the birth of Jesus. Chapters 10 to 12 treat of the crucifixion, resurrection, and ascension of Jesus of Nazareth. The final arguments are that Christianity is not contrary to Mosaic Law. Additionally, Petrus was a noted astronomer and translated scientific works from the Arabic.
Baer, Spain, 1 (1961), 59; Ashtor, Korot, 2 (1966), 172–3; G. Díaz-Plaja, Historia general de las literaturas hispámcas…, 1 (1949), 194, 285–6; J.M. Millás Vallicrosa, La Obra astronómica de Mosé Sefardi (1937); idem, in: Sefarad, 3 (1943), 65–105; F. Ainaud de Lasarte, ibid., 359–76; H. Schwarzbaum, ibid., 22 (1962), 17–59, 321–44; 23 (1963), 54–73; J.J. Jones and J.E. Keller, The Scholar's Guide (1969).
[Kenneth R. Scholberg]