THE SOLAR MODEL IN JOSEPH IBN JOSEPH IBN NAHMIAS'LIGHT OF THE WORLD

Abstract

In an influential article, A. I. Sabra identified an intellectual trend from twelfth and thirteenth-century Andalusia which he described as the ‘‘Andalusian revolt against Ptolemaic astronomy.” Philosophers such as Ibn Rushd (d. 1198 C. E.), Ibn Tufayl (d. 1185), and Maimonides (d. 1204) objected to Ptolemy’s (fl. 125–50) theories on philosophic grounds, not because of shortcomings in the theories' predictive accuracy. Sabra showed how al-Bitrūjī's (fl. 1200) Kitāb al-Hay'a (The Book of Astronomy) attempted to account for observed planetary motions in a way that met the philosophic standards of those philosophers and others. In Nūr al-‘ālam (Light of the World), the subject of this article, Joseph ibn Joseph ibn Nahmias (fl. ca. 1400) endeavoured to improve upon al-Bitrūjī’s models. Levi Ben Gerson's (1288–1344) Hebrew writings on astronomy criticized al-Bitrūjī, but Ibn Nahmias did not mention them. Nūr al-‘ālam deserves attention, too, because it is the first Arabic text on theoretical astronomy by a Jewish author to come to light. In the body of this article, I will describe and analyze Ibn Nahmias’ theory, from Nūr al-‘ālam, for the motion of the sun.