John of Seville
[3][4] John of Seville was a baptized Jew, whose Jewish name (now unknown) has been corrupted into "Avendeut", "Avendehut", "Avendar" or "Aven Daud".
The introduction of an effective method of marking alidades, an integral component of astrolabes, was introduced through one of John's translations titled Dixit Johannes: Cum volueris facere astrolabium accipe auricalcum optimum.
[11] Another work that is attributed to John of Seville through a note in the beginning of one of the margins is from Astroligi(c)e speculationis exercitium habere volentibus, which is now at Pommersfelden, near Bamberg in Germany.
[10] At least three of his translations, a short version of the Secretum Secretorum dedicated to a Queen Tarasia, a tract on gout offered to one of the Popes Gregory, and the original version of the 9th century Arabic philosopher Qusta ibn Luqa's De differentia spiritus et animae (The Difference Between the Spirit and the Soul), were medical translations intermixed with alchemy in the Hispano-Arabic tradition.
[3] A lesser-known translation of his titled Speculum Elementorum, also referred to as Tractatus de perfecta et infallibili Medicina arte Akimie, was originally written by an unknown author.
[14] 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: John of Seville is also credited with working in collaboration with Dominicus Gundissalinus and Jewish philosopher Abraham Ibn Daud to translate the De anima of Avicenna, a philosophical commentary on Aristotle's writings.
A work by Jewish philosopher Avencebrol is believed to be translated by both John of Seville and Dominicus Gundissalinus titled Fons Vitae (Source of Life).
[18] In addition to his many translations John of Seville is credited with a work of his own titled, Epitome artis astrologiae, written in 1142 which is a summary of astrology as a whole.
