His 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.
His commentary on the Bible was sharply criticized by the most prominent scholars, such as Abarbanel, Chisdai Crescas, and Rivash, the latter accusing him of heresy and almost banning his works.
His most important treatise, that by which he has a place in the history of philosophy, is entitled Sefer Milhamot Ha-Shem, ("The Wars of the Lord"), and occupied twelve years in composition (1317–1329).
"Whereas the earlier Jewish philosophers extended the omniscience of God to include the free acts of man, and had argued that human freedom of decision was not affected by God's foreknowledge of its results, Ibn Daud, evidently following Alexander of Aphrodisias, excludes human action from divine foreknowledge.
[6] Rabbi Yeshayahu Horowitz explained the apparent paradox of his position by citing the old question, "Can God create a rock so heavy that He cannot pick it up?"
[9] 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.
[10] 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.
Maaseh Hoshev is sometimes mistakenly referred to as Sefer Hamispar (The Book of Number), which is an earlier and less sophisticated work by Rabbi Abraham ben Meir ibn Ezra (1090–1167).
Gersonides was also 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.
Julius Guttman explained that for Gersonides, astrology was:founded on the metaphysical doctrine of the dependence of all earthly occurrences upon the heavenly world.
…The active intellect knows the astrological order, from the most general form of the constellations to their last specification, which in turn contains all of the conditions of occurrence of a particular event.
Thus, when a prophet deals with the destiny of a particular person or human group, he receives from the active intellect a knowledge of the order of the constellations, and with sufficient precision to enable him to predict its fate in full detail.
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.
[17] 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.
A (fictional) encounter between Gersonides and Pope Clement VI at Avignon during the Black Death is a major element in the book's plot.