The medieval Jewish scientist, philosopher, and theologian Levi ben Gershon (1288-ca. 1344), also called Gersonides and Leo Hebraeus, is known for his continuation of the Jewish Aristotelian tradition in philosophy and for his advanced scientific studies.
Levi ben Gershon was born at Bagnols in the Languedoc region of France. He derived from a scholarly family and probably supported himself by practicing medicine. He lived most of his life in the cities of Avignon, Orange, and Perpignan, where the Jews were protected by the papacy. The exact date of his death is unknown.
Modern historians admire Levi ben Gershon for the breadth of his knowledge and writings. He also reflects the close coincidence between Jewish and Christian philosophy in the later Middle Ages. Philosophers of both faiths reacted excitedly to the rediscovery of Aristotle's writings. In the 13th and 14th centuries, both Judaism and Christianity tried to reconcile faith and reason. Theologians of each religion tried to reconcile their faith to the pagan philosophy of Aristotle, although in each case reason lost out to faith in the 14th and 15th centuries.
Levi ben Gershon ranks as the most radical of Jewish Aristotelians, or, more properly, Averroists, the name applied to medieval philosophers who derived their knowledge of Aristotle from the Arab philosopher Averroës. Asan Averroist, Levi ben Gershon insisted that Judaism was compatible with Aristotle's teachings. When the two conflicted, he reinterpreted Jewish Scripture to its detriment, at least in the opinion of his opponents. They called his major work, Milhamot Adonai (Wars of the Lord), by a derogatory title: "Wars against the Lord."
More radical in his thinking than the outstanding Jewish Aristotelian, Maimonides, Levi ben Gershon marked the end of his school of thought. Both philosophers were attacked and rejected by such later writers as Hasdai Crescas. Levi ben Gershon wrote on many other subjects, in Hebrew, and admiring Christian scholars translated much of his work into Latin. His book on trigonometry was very advanced, and Pope Clement VI had it translated as De sinibus, chordis et arcubus. Levi ben Gershon improved the camera obscura, and he may have invented the cross-staff, which he called Jacob's staff, for measuring the altitude of stars. He also accomplished valuable astronomical work, although he rejected the heliocentric theory.
A distinguished Talmudist, Levi ben Gershon was a remarkably learned and intelligent man who materially advanced the science and philosophy of his period. Much of his scientific and philosophical thought is contained in his magnum opus, Milhamot Adonai.
The most informative book on Levi ben Gershon and his philosophical tradition is Isaac Husik, A History of Medieval Jewish Philosophy (1916). For the milieu in which Levi ben Gershon lived see S. W. Baron, A Social and Religious History of the Jews, vol. 8 (1969).