Astronomer, mathematician, and philosopher. Born in France, he commented on the Bible, Aristotelian philosophy, and the Talmud. He devised an instrument used in navigation for measuring angular separation between astronomical bodies. His major philosophical work, Milhamot Adonai, deals with contemporary Jewish philosophical questions. His views were controversial because, unlike Maimonides, he did not always let the Bible be the final word when facing a contradiction between Judaism and Greek philosophy.