CRESCAS, ḤASDAI (c. 1340–1410/11), Spanish rabbi, philosopher, natural scientist; author of the anti-Aristotelian Hebrew classic, Or Adonai (The Light of the Lord). Son of a distinguished family of scholars and merchants, Crescas was raised in Barcelona, studying there under the renowned Talmudist and homilist Nissim ben Re'uven. He served as rabbi in Barcelona and from 1387 was an adviser to the king and queen of Aragon, Joan I and Violant. In 1389, Crescas assumed the post of rabbi of Saragossa, and the next year he was recognized by the throne as judge of all the Jews of Aragon. Following the anti-Jewish mob riots of 1391, in which thousands of Spanish Jews—including his only son—were murdered and more than a hundred thousand were converted to Christianity, he devoted himself to the physical and spiritual reconstruction of the Jewish communities of Aragon and of Spain as...