22 Facts About Gersonides

Gersonides's family had been distinguished for piety and exegetical skill in Talmud, 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.

Gersonides 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.

Gersonides is known for his unorthodox views and rigid Aristotelianism, which eventually led him to rationalize many of the miracles in the Bible.

Gersonides makes reference to a commentary on Isaiah, but it is not extant.

In contrast to the theology held by other Jewish thinkers, Jewish theologian Louis Jacobs argues, Gersonides held that God does not have complete foreknowledge of human acts.

Gersonides posits that people's souls are composed of two parts: a material, or human, intellect; and an acquired, or agent, intellect.

Gersonides was the author of the following Talmudic and halakhic works:.

Gersonides was the first to make a number of major mathematical and scientific advances, though since he wrote only in Hebrew and few of his writings were translated to other languages, his influence on non-Jewish thought was limited.

Gersonides wrote Maaseh Hoshev in 1321 dealing with arithmetical operations including extraction of square and cube roots, various algebraic identities, certain sums including sums of consecutive integers, squares, and cubes, binomial coefficients, and simple combinatorial identities.

In 1342, Gersonides wrote On Sines, Chords and Arcs, which examined trigonometry, in particular proving the sine law for plane triangles and giving five-figure sine tables.

Gersonides is credited to have invented the Jacob's staff, an instrument to measure the angular distance between celestial objects.

Gersonides described a geometrical model for the motion of the Moon and made other astronomical observations of the Moon, Sun and planets using a camera obscura.

Gersonides was the earliest known mathematician to have used the technique of mathematical induction in a systematic and self-conscious fashion and anticipated Galileo's error theory.

Gersonides believed that astrology was real, and developed a naturalistic, non-supernatural explanation of how it works.

Gersonides appears to be the only astronomer before modern times to have surmised that the fixed stars are much further away than the planets.

Whereas all other astronomers put the fixed stars on a rotating sphere just beyond the outer planets, Gersonides estimated the distance to the fixed stars to be no less than 159,651,513,380,944 earth radii, or about 100,000 lightyears in modern units.

Ne'eman argued that after Gersonides reviewed Ptolemy's model with its epicycles he realized that it could be checked, by measuring the changes in the apparent brightnesses of Mars and looking for cyclical changes along the conjectured epicycles.

Gersonides developed tools for these measurements, essentially pinholes and the camera obscura.

That challenge was finally answered, of course, by Copernicus and Kepler three centuries later, but Gersonides was the first to falsify the Alexandrian dogma - the first known instance of modern falsification philosophy.

Gersonides showed that Ptolemy's model for the lunar orbit, though reproducing correctly the evolution of the Moon's position, fails completely in predicting the apparent sizes of the Moon in its motion.

Unfortunately, there is no evidence that the findings influenced later generations of astronomers, even though Gersonides' writings were translated and available.

Gersonides is an important character in the novel The Dream of Scipio by Iain Pears, where he is depicted as the mentor of the protagonist Olivier de Noyen, a non-Jewish poet and intellectual.