John of Seville

John of Seville (Latin: Johannes Hispalensis or Johannes Hispaniensis) was the main translator from Arabic into Castilian together with Dominicus Gundissalinus during the early days of the Toledo School of Translators. His work is said to have flourished between 1135 and 1153.
He was a baptized Jew, whose Jewish name (now unknown) has been corrupted into "Avendeut", "Avendehut", "Avendar" or "Aven Daud". This evolved into the middle name "David", so that, as a native of Toledo, he is frequently referred to as Johannes (David) Toletanus. Some historians argue that in fact there were two different persons with a similar name, one as Juan Hispano (Ibn Dawud) and other as Juan Hispalense, this last one perhaps working at Galician Limia (Ourense), for he signed himself as "Johannes Hispalensis atque Limiensis", during the Reconquista, the Christian campaign to regain the Iberian Peninsula.
The topics of his translated works were mainly astrological and astronomical, philosophical and medical. At least three of his translations, the Secretum Secretorum dedicated to a Queen T[arasia?], a tract on gout offered to one of the Popes Gregory, and the original version of the 9th century Arabic philosopher Costa ben Luca's De differentia spiritus et animae, were medical translations intermixed with alchemy in the Hispano-Arabic tradition. In his Book of Algorithms on Practical Arithmetic, John of Seville provides one of the earliest known descriptions of Indian positional notation, whose introduction to Europe is usually associated with the book Liber Abaci by Fibonacci:
“A number is a collection of units, and because the collection is infinite (for multiplication can continue indefinitely), the Indians ingeniously enclosed this infinite multiplicity within certain rules and limits so that infinity could be scientifically defined; these strict rules enabled them to pin down this subtle concept.”
John of Seville translated Al-Farghani's Kitab Usul 'ilm al-nujum(Book on the Elements of the Science of Astronomy) into Latin in 1135 ('era MCLXXIII'), as well as translating the Arab astrologer Albohali's "Book of Birth" into Latin in 1153. He also translated Kitāb taḥāwīl sinī al-‘ālam by Abu Ma'shar al-Balkhi into Latin.