Levi ben Gershon (1288–1344), better known by his Latinised name as Gersonides or the abbreviation of first letters as RaLBaG, was a philosopher, Talmudist, mathematician and astronomer/astrologer. He was born at Bagnols in Languedoc, France. According to Abraham Zacuto and others, he was the son of Gerson ben Solomon Catalan.

Read more about Gersonides:  Biography, Estimation of Stellar Distances and Refutation of Ptolemy's Model, Talmudic Works, In Modern Fiction, Bibliography