'''Pedro Alfonso''', juga dikenal sebagai '''Moshe Sephardi''' (Huesca, Spanyol, 1062-1140) adalah seorang Yahudi Spanyol yang berprofesi sebagai penulis dan ahli astronomi.

Ia adalah dokter dari dibaptiskan menjadi seorang Kristen pada hari Santo Petrus, 29 Juni 1106, Raja Alfonso I menjadi wali baptisnya. Dalam kesempatan itu ia mengganti namanya menjadi Petrus Alfonsi ("Petrus kepunyaan Alfonso").

Pedro Alfonso menuliskan mengenai perubahan religinya itu dalam bukunya ''Dialogus contra iudaeos'', dalam bahasa Latin. Di sini ia menuliskan serangkaian dialog melawan orang-orang Yahudi, dalam suatu dialog antara Mose dan Pedro (yaitu Moses Sephardi dan Petrus Alfonsi, artinya dia sendiri sebelum dan sesudah pindah agama). Dalam karya yang sama ia menuliskan bahwa ia pergi ke negara Inggris sebagai "magister" dalam seni liberal dan dalam astronomi, lulusan dari biara Malvern, dengan mempelajari sistem astronomi Arab dalam kelulusannya.

Karya besarnya adalah sebuah koleksi novel-novel, tiga puluh tiga cerita yang dituliskan dalam bahasa Latin: ''Disciplina Clericalis'' (Sekolah Pelatihan Pendeta). Koleksi ini diterjemahkan dalam bahasa Arab, Persia kuno, dan Hindi.

thumb|Petrus Alfonsi's [[Tetragrammaton-Trinity diagram, which influenced Joachim of Fiore and the development of the Shield of the Trinity diagram.]]

'''Petrus Alphonsi''' (also known as Peter Alfonsi; born '''Moses Sepharadi''') (Spanish writer and astronomer, and polemicist, who converted to Christianity. He was physician to King Alfonso VI of Castile.

Alphonsi was born at baptized at godfather he took the name of Petrus Alfonsi (Alfonso's Peter). 
<br />
Petrus was born a Jew while living in al-Andalus, and after he rose to prominence, he converted to Christianity.  This environment gave him an advantageous knowledge of Christianity, Judaism, and Islam that would later prove useful in his polemics. John Tolan mentioned in his book Petrus Alfonsi and His Medieval Readers that “Alfonsi’s texts were received enthusiastically—he became an auctor, an authority to be quoted. His success was due in large part to his ability to bridge several cultures: a Jew from the [Muslim] world of al-Andalus.”  His knowledge of these different religions is what makes Alfonsi unique and why he is essential to be studied when looking at anti-Judaic polemics.<br />
	Petrus’ upbringing placed him in an atmosphere that provided a significant impetus to launch him as one of the most important figures in anti-Judaic polemics. According to Tolan, Petrus Alfonsi was reared in a society in turmoil: a place of chaos and political instability, where Judaism was in conflict with science, and Islam and Christianity were becoming a larger influence.  His background was conveniently placed in the center of contention between religions and circumstances that surrounded his upbringing, and provided the framework for polemics that would shape Medieval Judaic perception.

==In England==
In the ''Dialogus'' Alphonsi relates that he traveled to England as ''magister'' in liberal arts. He spent several years there.<ref>[http://www.muslimheritage.com/uploads/IslamicScienceAndEngland.pdf PDF]; perhaps 1112 to 1120.</ref> He may have been a court physician of Henry I of England.
 
The presence of Alfonsi in the West Country in the years before that date may have contributed to the flowering of Arabic science in that region from the 1120s onwards.<ref>Oxford Dictionary of National Biography, art. "Alfonsi, Petrus"</ref> He discussed astronomy with Walcher of Malvern. Petrus passed on the Arabic system of astronomical graduation.<ref>[http://www.medievalhistory.net/islamica.htm]</ref> They may have collaborated on a work on eclipses.<ref>[http://www.nd.edu/~mdowd1/disschapters/Chap1.Background.pdf PDF], p.19.</ref>

==Works==
===''Disciplina Clericalis''===
Alfonsi's fame rests chiefly on a collection of thirty-three tales, composed in Latin. This work is a collection of oriental tales  of moralizing character, translated from Arabic, old Persian and Hindi. It established some didactic models that would be followed by other medieval authors. 

The collection enjoyed remarkable popularity, and is an interesting study in Caxton's translation of the fables of Æsop, where thirteen apologues of "Alfonce" are taken in fact from the ''Disciplina Clericalis''.<ref>Jacobs, Jewish Ideals, 1896, pp. 141-143. He lays stress on Alfonsi's importance as one of the intermediaries between Eastern and Western folk-lore, and quotes one of Caxton's stories from "Alfonce."</ref>

An outline of the tales, by Douce, is prefixed to Ellis' "Early English Metrical Romances." Nearly all the stories are adopted in the ''Gesta Romanorum''. Chapters ii and iii were done into Hebrew and issued under the title, ''Book of Enoch,'' <ref>Constantinople, 1516; Venice, 1544 and 1605.</ref>. An early French translation of this Hebrew language extract was made prior to 1698 by Piques, and August Pichard published another version in Paris, 1838.

Friedrich Wilhelm Valentin Schmidt produced a scholarly edition in 1827.<ref>[http://www.newadvent.org/cathen/11783a.htm]: ''Labouderie, Vicar-General of Avignon, published it at Paris in 1824 with a French translation of the fifteenth century.''</ref>

===Controversial writings===
Like many converts of his time, Alphonsi was accused of bad faith by the Jewish community<ref></ref> and to counter this, as well as to show his zeal for his new faith he wrote a work attacking Judaism and defending the truths of the Christian faith. The work is praised by Raymund Martin, in his ''Pugio Fidei'', and others, but it is little known today. Steinschneider observed (<ref>"Hebr. Uebers." p. 933</ref>) that it merited the oblivion into which it has fallen, while Gröber termed it "the most important literary apologia for Christian, as opposed to Jewish, beliefs ever written,"<ref>G. Gröber, Übersicht über d. Lat. Lit. von. d. Mitte d. 6. Jhs. bis zur Mitte d. 14. Jhrs., Munich, 1963, sect. 130, p. 232</ref> and Manitius praised the "distinguished repose of its oriental powers of reasoning and persuasion."<ref>M. Manitius, Geschichte d. lateinischen Literatur des Mittelalters, Munich, 1931, vol. III, p. 274</ref> The ''Dialogi in quibus impiæ Judæorum ... opiniones ... confutantur'',<ref>Full title in Wolf, "Biblioteca Hebræa" (i. 971) and Fürst, "Bibl. Jud." (i. 36).</ref> appeared at Cologne in 1536 and later in "Biblioteca Patrum". <ref>xii. 358, xxi.; ed. Lugdunensis, p. 172; ed. Migne, t. 157, p. 535).</ref> Other books are ascribed to him, and he is sometimes confounded with Petrus Hispanus of the thirteenth century. See Steinschneider<ref>l.c. p. 470, § 282; p. 934, § 557, note 208.</ref>, who regards him as the probable translator of the ''Canones Tabularum''<ref>"Cod. Corp. Chr." 283, 13; f. 141b.</ref> from the Arabic. It is ascribed to one Petrus Anfulsus, who is very likely identical with Alfonsi<ref>See Steinschneider, "Hebr. Bibl." 1882, xxi. 38; "Hebr. Uebers." pp. 985, 986, § 589.</ref>.

Another controversial tract, described as a dialogue "Inter Petrum Christianum et Moysem Hæreticum"<ref>Codex Merton, 175b, f. 281; in Coxe's "Cat." p. 69.</ref>, is said to have been written by Petrus Alphonsi<ref>Compare "Hebr. Bibl." xxi. 38.</ref>. In Cambridge University, England, there is a manuscript of the fifteenth century bearing the title: "De Conversione Petri Alfonsi Quondam Judæi et Libro Ejus in Judæos et Saracenos," which is mentioned in Steinschneider's "Polemische und Apologetische Literatur," 1877, p. 224<ref>Compare p. 235, No. 5, s.v. Epistola.</ref>.

===Dialogi contra Iudaeos===

The most controversial writing was the ''Dialogi contra Iudaeos''. It is a disputation, and it is written in twelve separate divisions called ''tituluses'' where the first four attacked Judaism, the last seven defended Christianity, and the fifth ''titulus'' argued against Islam. 

Up until the ''Dialogi contra Iudaeos'', the Augustinian tradition was followed in Christendom which allowed relative tolerance to the Jewish people, and for the most part up until this point the attacks on the Jewish people were localized and more importantly, not organized. There was no literature before Petrus Alfonsi’s ''Dialogi'' condemning Judaism as a whole. There was no document for people to latch on to and group up against the Jewish people.

Petrus’ polemics were offensive in nature, and attempted to prove Christianity by disproving Judaism. The difficulty in proving Christianity through the invalidity of Judaism is that the basic tenants of Christianity originate in the Old Testament; if a polemicist proves the Old Testament is invalid, then ''ipso facto'' he also proves the invalidity of Christianity. Petrus attempted to avoid this problem, and refutes Judaism with their own weapons  by challenging the Talmud and rabbis. 

This work presented a point of view contrary to previous Christian philosophy because Christians claimed that the Jews were blindly practicing the Old Law.  Petrus Alfonsi initiated a differing idea that “the Jews no longer followed the Old Law; they follow a new and heretical law, that of the Talmud.”  Petrus’ belief was that the Jewish leaders were knowingly and willfully leading their flock astray. He believed that they purposely lied in order to conceal their sin of killing Jesus, in spite of the fact that they knew that he was the Son of God. Petrus Alfonsi also claimed that the Talmud was written to keep the Jewish people from seeing that Jesus was the Son of God; he called the Talmud “a fabric of lies” and a “heretical book.” <br />

What makes this doctrine so radically different from previous Christian polemics is that they tried to prove the validity of Christianity by pointing out scriptures in the Old Law that confirmed that Jesus was the Son of God. With this belief, it portrayed the Jews as a people who would eventually see the truth and would ultimately convert to Christianity. Petrus’ new concept claimed that the Jewish leaders were blatantly lying and had attempted to cover up the truth. This new concept obviously would create a new type of tension between Christians and Jews.

The Augustinian tradition afforded Jews in Europe a tolerance throughout the Latin West that was not shared among other religions.  This tradition did not place any emphasis on Judaism being heretical, but rather pointed to the fact that the Jews had a pivotal part to play in the spreading of Christianity. This doctrine was originally written to explain why Jews were not converting to Christianity. Since the Jews were the ones who had kept the law, it would seem logical that they would know whether the savior had come, and this presented a problem within Christian society. Daniel Lasker said of Petrus’ ideology that “These innovations signaled the beginning of the end of the relative Christian tolerance of Jews and Judaism inspired by the writings of Augustine.”  Other authors before Petrus had used harsher rhetoric; there was seldom any deviation from the Augustinian tradition.  