GERSONIDES, or BEN GERSON (GERSHON), LEVI, known also as RALBAG (1288-1344), Jewish philosopher and commentator, was born at Bagnols in Languedoc, probably in 1288. As in the case of the other medieval Jewish philosophers little is known of his life. His family had been distinguished for piety and exegetical skill, but though he was known in the Jewish community by commentaries on certain books of the Bible, he never seems to have accepted any rabbinical post. Possibly the freedom of his opinions may have put obstacles in the way of his preferment. He is known to have been at Avignon and Orange during his life, and is believed to have died in 1344, though Zacuto asserts that he died at Perpignan in 1370. Part of his writings consist of commentaries on the portions of Aristotle then known, or rather of commentaries on the commentaries of Averroes. Some of these are printed in the early Latin editions of Aristotle's works. His most important treatise, that by which he has a place in the history of philosophy, is entitled _Milhamoth 'Adonai_ (The Wars of God), and occupied twelve years in composition (1317-1329). A portion of it, containing an elaborate survey of astronomy as known to the Arabs, was translated into Latin in 1342 at the request of Clement VI. The _Milhamoth_ is throughout modelled after the plan of the great work of Jewish philosophy, the _Moreh Nebuhim_ of Moses Maimonides, and may be regarded as an elaborate criticism from the more philosophical point of view (mainly Averroistic) of the syncretism of Aristotelianism and Jewish orthodoxy as presented in that work. The six books pass in review (1) the doctrine of the soul, in which Gersonides defends the theory of impersonal reason as mediating between God and man, and explains the formation of the higher reason (or acquired intellect, as it was called) in humanity,--his view being thoroughly realist and resembling that of Avicebron; (2) prophecy; (3) and (4) God's knowledge of facts and providence, in which is advanced the curious theory that God does not know individual facts, and that, while there is general providence for all, special providence only extends to those whose reason has been enlightened; (5) celestial substances, treating of the strange spiritual hierarchy which the Jewish philosophers of the middle ages accepted from the Neoplatonists and the pseudo-Dionysius, and also giving, along with astronomical details, much of astrological theory; (6) creation and miracles, in respect to which Gerson deviates widely from the position of Maimonides. Gersonides was also the author of a commentary on the Pentateuch and other exegetical and scientific works.