page_title: Petrus Alphonsi
hierarchical_section_title: Petrus Alphonsi
caption_attribution_description: A diagram on the Tetragrammaton (divine four-letter name) YHWH (Hebrew יהוה) — or "IEVE" as it's transcribed into the Latin language here — as a foundation of the Christian Trinity. This is taken from a 12th-century manuscript of the ca. 1109 A.D. work Dialogi Contra Iudaeos ("Dialogues against the Jews") by Petrus Alphonsi / Petrus Alfonsi / Peter Alfonsi (a convert to Christianity from Judaism). The diagram shows the three persons of the Christian Trinity assigned to the three possible consecutive two-letter sequences of the Tetragrammaton YHWH / IEVE — namely IE, EV, and VE. These three sequences are in three circular nodes, connected to each other by three lines making a triangle. In the center, supported by fanciful animals, is a scroll with the complete Tetragrammaton. (The fanciful animals would not have been present in Petrus Alfonsi's original version of the diagram, but were probably a personal decorative addition by the scribe who copied out this particular manuscript of the Dialogues.) The current-day relevance of this diagram is mainly that it influenced the development of the later "Shield of the Trinity" or "Scutum Fidei" diagram, as well as influencing Joachim of Fiore's own different IEUE interlaced circles diagram (which in turn led to the use of the Borromean rings as a symbol of the Christian Trinity).[1]
context_page_description: Petrus Alphonsi was a Jewish Spanish physician, writer, astronomer, and polemicist, who converted to Christianity in 1106. He is also known just as Alphonsi, and as Peter Alfonsi or Peter Alphonso and was born Moses Sephardi. Born in Islamic Spain, he mostly lived in England and France after his conversion.
  He was born at an unknown date and place in the 11th century in Spain, and educated in al-Andalus, or Islamic Spain. As he describes himself, he was baptised at Huesca, capital of the Kingdom of Aragon, on St. Peter's Day, 29 June 1106, when he was probably approaching middle age; this is the first clear date we have in his biography. In honor of the saint Peter, and of his royal patron and godfather, the Aragonese King Alfonso I he took the name of Petrus Alfonsi.
  By 1116 at the latest he had emigrated to England, where he seems to have remained some years, before moving to northern France. The date of his death is as unclear as that of his birth. He was famous as a writer during his lifetime, and remained so for the rest of the Middle Ages, with over 160 surviving medieval manuscripts containing works of his.
context_section_description: Petrus Alphonsi was a Jewish Spanish physician, writer, astronomer, and polemicist, who converted to Christianity in 1106.  He is also known just as Alphonsi, and as Peter Alfonsi or Peter Alphonso and was born Moses Sephardi).  Born in Islamic Spain, he mostly lived in England and France after his conversion.
  He was born at an unknown date and place in the 11th century in Spain, and educated in al-Andalus, or Islamic Spain.  As he describes himself, he was baptised at Huesca, capital of the Kingdom of Aragon, on St. Peter's Day, 29 June 1106, when he was probably approaching middle age; this is the first clear date we have in his biography. In honor of the saint Peter, and of his royal patron and godfather, the Aragonese King Alfonso I he took the name of Petrus Alfonsi (Alfonso's Peter).
  By 1116 at the latest he had emigrated to England, where he seems to have remained some years, before moving to northern France. The date of his death is as unclear as that of his birth.  He was famous as a writer during his lifetime, and remained so for the rest of the Middle Ages, with over 160 surviving medieval manuscripts containing works of his.  The most common are his Dialogi contra Iudaeos (Dialogue Against the Jews), an imaginary conversation between a Jew and a Christian, and Disciplina Clericalis (A Training-school for the Clergy), in fact a collection of Eastern fables.
  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.
  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 centre of contention between religions and circumstances that surrounded his upbringing, and provided the framework for polemics that would shape Medieval Judaic perception.
caption: Petrus Alfonsi's Tetragrammaton-Trinity diagram, which influenced Joachim of Fiore and the development of the Shield of the Trinity diagram.
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