Abner of Burgos (c. 1270 – c. 1347, or a little later) was a Jewish philosopher, a convert to Christianity and a polemical writer against his former religion. Known after his conversion as Alfonso of Valladolid or "Master Alfonso."


As a student he acquired a certain mastery in Biblical and Talmudical studies, to which he added an intimate acquaintance with Peripatetic philosophy and astrology. What we know of his biography comes primarily from his own comments in his Moreh Zedek/Mostrador de justicia. According to that work, he stated that his religious doubts arose in 1295 when he treated a number of Jews for distress following their involvement in the failed messianic movement in Avila. As Abner tells it, he "had a dream" in which a similar experience of crosses mysteriously appearing on his garments drove him to question his ancestral faith.[1]

Not being of those contented ones who, as Moses Narboni observes in his Maamar ha-Beḥirah (Essay on the Freedom of the Will; quoted by Grätz, p. 488), are satisfied with a peck of locust beans from one Friday to another, he resolved to embrace Christianity. The timing of his conversation is uncertain, but probably occurred around 1320. Pablo de Santa María (Scrutinium Scripturarum) suggests the event occurred when Abner/Alfonso was of the advanced age of sixty. According to the statements of his contemporaries such as Narboni, he converted, not from spiritual conviction, but for the sake of temporal advantage. Something of the apostate's pricking conscience seemed to have remained with him, despite his being immediately rewarded with a sacristan's post in the prominent Metropolitan Church in Valladolid (from where he took the name of Alfonso of Valladolid). The argument that Abner converted for material gain is put into question by the fact that his post as a sacristan was extremely modest and he never, throughout his long and public polemical career after conversion (c. 1320–1347), advanced in his post to something more lucrative (as did Pablo de Santa María, for example).


Abner/Alfonso's most distinguishing characteristic was his use of post-biblical literature, including hundreds of Talmudic and Midrashic sources as well as much medieval Jewish and Arabic (in translation) literature, all in an effort to prove the truth of Christianity. Equally striking was that he wrote his anti-Judaism polemics in Hebrew, unlike virtually every polemicist in the history of Christianity. His most important work, the Moreh Zedek (Teacher of Righteousness), which now survives only in a 14th-century Castilian translation as Mostrador de Justicia, is one of the longest and most elaborate polemics against Judaism ever written and is considered one of the key sources for the history of anti-Jewish thought in fourteenth century Western Europe. Abner/Alfonso's text rivals (and in many ways surpasses) the Ramon Martí's Pugio Fidei in length, complexity, variety of sources and psychological impact, although there is no evidence that Abner/Alfonso actually knew of the polemical Dominican's work. A comparison of their respective treatment of similar questions suggests that Abner/Alfonso did not know the work of Martí directly.

In an essay entitled Minhat Qenaot (A Jealousy Offering), he argued that man's actions are determined by planetary influence, and he reinterpreted the notion of choice and free will in light of that determinism. Both his conversion and this defence of determinism aroused protests from his Jewish former study-partner, Isaac Pulgar, marked by great bitterness. Abner also exchanged a number of polemical letters with local Jews, which have survived along with each of their responses and the final riposte to all the letters by Abner, a short work known as the Teshuvot ha-Meshubot.

Abner presented charges before Alfonso XI of Castile, accusing his former brethren of using the Birkat haMinim, a prayer-formula in their ritual, which blasphemed the Christian God and cursed all Christians. The king ordered a public investigation at Valladolid, in which the representatives of the Jewish community were confronted by Abner. The conclusion was announced in the form of a royal edict forbidding the use of the formula in question (February 1336). Abner further accused the Jews of constantly warring among themselves and splitting into hostile religious schisms. In support of this statement he came up with an alleged list of the "sects" prevailing among them: Sadducees, Samaritans, and other divisions. He makes two "sects" of Pharisees and Rabbinites, stated that cabalists believed in a tenfold God, and spoke of a brand-new "sect" believing in a dual Deity, God and Metatron.


The following is a list of Abner's writings:

  1. The Moreh Zedek (Teacher of Righteousness), surviving only as the Mostrador de justicia (Paris BN MS Esp. 43, consisting of a dialogue containing ten chapters of discussions between a religious teacher (Abner?) and a Jewish controversialist.
  2. Teshuvot la-Meharef (Response to the Blasphemer), also in Castilian translation, Respuestas al blasfemo (Rome. Biblioteca Apostolica Vaticana MS 6423)
  3. Polemical letters and the Teshuvot ha-Meshubot responding to responses to his letters.
  4. The Libro de la ley
  5. The determinist philosophical work Minhat Qenaot (Offering of Zeal), surviving only in Castilian translation as Ofrenda de Zelos or Libro del Zelo de Dios (Rome. Biblioteca Apostolica Vaticana MS 6423)
  6. A Mathematical treatise Meyyasher Aqob (Straightening the Curve) (attributed)

Some of his lost works may include:

  1. A commentary on Ibn Ezra's commentary on the Decalogue, written before his apostasy.
  2. ''Sefer Milhamot Adonai ("Wars of the Lord"). This was translated into Castilian, at the request of the Infanta Doña Blanca, prioress of a convent in Burgos, under the title "Las Batallas de Dios."
  3. La Concordia de las Leyes, an attempt to provide Old Testament foundations for Christian dogmas. According to Reinhardt and Santiago (p. 86, n. 10.4) this text is found in Paris BN MS Esp. 43.
  4. Iggeret ha-Gezerah (Epistle on Fate).

Some of the works falsely attributed to him include:

  1. Libro de las tres gracias, Madrid Biblioteca Nacional MS 9302 (Kayserling). The title is a misreading of Libro de las tres creencias. According to Reinhardt and Santiago (pp. 86–88, n. 10.5) the text is also found in Escorial MSS h.III.3 and P.III.21, where it is called the Libro declarante.
  2. Libro de las hadas (also attributed to the Pseudo-San Pedro Pascual). According to Reinhardt and Santiago (p. 88, n. 10.6) this text is also found in Escorial MSS h.III.3 and P.III.21
  3. Sermones a los moros y judios. Found as anonymous in Soria: Casa de la Cultura, MS 25-H (Reinhardt and Santiago, p. 314, n. 143.6)
  4. The Epistola Rabbi Samualis and Disputatio Abutalib of Alfonsus Bonihiminis.

See also


  1. ^ Ryan Szpiech, Conversion and Narrative: Reading and Religious Authority in Medieval Polemic (Philadelphia: University of Pennsylvania Press, 2013, chapter 5, pp. 143–73


---. "From Testimonia to Testimony: Thirteenth-Century Anti-Jewish Polemic and the Moreh Zedek/Mostrador de justicia of Abner of Burgos/ Alfonso of Valladolid." Diss. Yale University, 2006.