The role of Jābir b. Aflaḥ’s Iṣlāḥ al-Majisṭī in the so called «Andalusian revolt against Ptolemaic astronomy»

Abstract

Jābir b. Aflaḥ al-Ishbīlī, known as Geber filius Afflay Hispalensis in medieval Western Europe, was a mathematician and theoretical astronomer who most probably flourished in Seville during the first quarter of the 12^th century. Jābir b. Aflaḥ was a leading figure in medieval astronomy thanks to the Iṣlāḥ al-Majisṭī, his magnum opus, which was translated into Latin and Hebrew. With his Iṣlāḥ al-Majisṭī, Jābir b. Aflaḥ intended to rewrite the Almagest and introduced some corrections to it. In his important paper «The Andalusian revolt against Ptolemaic astronomy» published in 1984, the renowned scholar A.I. Sabra drew attention to a group of Andalusian philosophers who where contemporaries of Jābir b. Aflaḥ or flourished shortly after him, such as Ibn Bājja (d. 537/1138), Ibn Ṭufayl (d. 581/1185), Ibn Rushd (d. 595/1198), Maimonides (d. 601/1204) and al-Biṭrūjī(fl. 596/1200). Sabra stressed their cosmological criticisms of the astronomical models described in the Almagest arising from the lack of consistency of Ptolemy’s models with Aristotle’s physics. The purpose of this paper is to describe Jābir b. Aflaḥ’s criticisms of Ptolemy in order to consider whether he should be placed among the members of the Andalusian revolt against Ptolemaic astronomy. The final conclusion is that Jābir b. Aflaḥ’s criticisms are not themselves cosmological — although they may have cosmological implications — but of a completely technical mathematical nature. He should not, therefore, be placed among the members of the Andalusian revolt against Ptolemaic astronomy.