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Hasdai ben Abraham Crescas (Catalan: [h?z'ðaj '?e? ?u'ða 'k?esk?s]; Hebrew: ; c. 1340 in Barcelona, Catalonia - 1410/11 in Zaragoza, Aragon) was a Catalan-Jewish philosopher and a renowned halakhist (teacher of Jewish law). Along with Maimonides ("Rambam"), Gersonides ("Ralbag"), and Joseph Albo, he is known as one of the major practitioners of the rationalist approach to Jewish philosophy.
Hasdai Crescas came from a family of scholars. He was the grandson of the Talmudist Hasdai ben Judah Crescas, and a disciple of the Talmudist and philosopher Nissim ben Reuben, known as The RaN. Following in the footsteps of his teacher he became a Talmudic authority and a philosopher of great originality. He is considered important in the history of modern thought for his deep influence on Baruch Spinoza.
After leaving Barcelona, he held the administrative position of crown rabbi in Aragon. He seems to have been active as a teacher. Among his fellow students and friends, Isaac ben Sheshet (known as the RIBaSH), famous for his responsa, takes precedence. Joseph Albo is the best known of his pupils, but at least two others have won recognition, Rabbi Mattathias of Saragossa, and Rabbi Zechariah ha-Levi.
Crescas was a man of means. As such he was appointed sole executor of the will of his uncle Vitalis Azday by the King John I of Aragon in 1393. Still, though enjoying the high esteem even of prominent non-Jews, he did not escape the common fate of his coreligionists. Imprisoned with his teacher upon a false accusation of host desecration in 1378, he suffered personal indignities because he was a Jew. His only son died in a massacre in Barcelona in 1391, a martyr for his faith, during the anti-Judaic persecutions of that period. Nevertheless, he kept his faith.
Notwithstanding this bereavement, his mental powers were unbroken; for the works that have made him famous were written after that terrible year. Another episode of his life worthy of note is connected with the appearance of the pseudo-Messiah of Cisneros, one of whose adherents he became. In 1401-02 he visited Joseph Orabuena at Pamplona at the request of the King of Navarre, who paid the expenses of his journey to various Navarrese towns (Jacobs, l.c. Nos. 1570, 1574). He was at that time described as "Rav of Saragossa."
His works on Jewish law, if indeed ever committed to writing - have not reached us. But his concise philosophical work Or Adonai, The Light of the Lord became a classical Jewish refutation of medieval Aristotelianism, and a harbinger of the scientific revolution in the 16th century.
Three of his writings have been preserved: