Spanish philosopher, Talmudic scholar, and critic of the Aristotelian rationalist tradition in Jewish thought, who became crown rabbi of Aragon.

A merchant and Jewish communal leader in Barcelona (1367), Crescas became closely associated with the royal court of Aragon after the accession of John I (1387) and was accorded the title “member of the royal household.” Empowered by royal decree to exercise over the Jewish community juridical and executive jurisdiction enumerated by Jewish law, he settled in Saragossa as the crown's chief rabbi.

Crescas' first known work is a chronicle of the massacres of Jews (including his son) in Barcelona in 1391, written in the form of a letter to the Jewish community of Avignon (now in France). Motivated to reaffirm Jewish principles during severe persecution of the Jews in Spain, he wrote (1397–98) a treatise in “Refutation of the Principles of the Christians,” a critique of 10 principles of Christianity.

Crescas' closely reasoned critique of Aristotle and Jewish Aristotelian tradition, represented in particular by the 12th-century philosopher Maimonides (Maimonides, Moses), is contained in his Or Adonai (“The Light of the Lord”), completed in 1410. In the work, a commentary on various aspects of the Torah, he rejected traditional proofs for the existence of God, insisting that certainty in this matter rests only on the authority of the Bible in stating “Hear, O Israel: The Lord our God is one Lord” (Deut. 6:4).