Abraham bar Hiyya, a 12th century Jewish scholar in Northern Spain, produced the first extensive work in Hebrew on the fixed Hebrew calendar, Sefer ha-Ibbur, the Book of Intercalation, around 1120. At the time, the fixed Hebrew calendar had already been in use for a few centuries. In order to determine possible incentives to write the work at that particular time we analysed Chapter 5 of Part III. The results suggest that the text is an apologetic and polemical work the composing of which was instigated by the presence of Karaite Jews, who did not accept Rabbinic authority.
Rabbi Abraham ibn Ezra, a 12th-century Spanish-born Jewish scientist and exegete, spent much of his life travelling through Latin Christendom teaching its Jews the Arabic sciences of al-Andalus. In his biblical commentaries, he expounded the relationships between rabbinic tradition and the science of astrology, but he also wrote technical, astrological textbooks in which questions of religion are treated only in the form of astrologically defined nationalities. In this paper, I intend to examine ibn Ezra's views on the interrelationships between the three traditions of astronomy, astrology, and revealed religion, as they appear in both his biblical commentaries and his astrological textbooks.