Saadia ben Joseph al-Fayumi (säˈdēä, äl-fĪyōˈmē) [key], 882–942, Jewish scholar, b. Egypt. He was known as Saadia Gaon. He was the head of the great Jewish Academy at Sura, Babylonia, which under his leadership became the highest seat of Jewish learning, and a vigorous opponent of the Karaites. Saadia's Book of Language laid the foundation of Hebrew grammar; he also wrote a Hebrew dictionary, the Agron, and made an Arabic translation of the Old Testament that became the standard version for all Arabic-speaking Jews and exerted an important influence upon Muslims as well. He also compiled the first comprehensive siddur (daily prayerbook). His great philosophical work is The Book of Beliefs and Opinions (tr. Samuel Rosenblatt, 1948). Writing in a period of spiritual doubt and confusion, Saadia attempts in this work to defend Jewish religious faith on the basis of rational argument, using the methods of Islamic speculative theology known as kalam. The first defense of Judaism in rational terms, Saadia's work laid the basis for all subsequent Jewish philosophy.
See S. L. Skoss, Saadia Gaon, the Earliest Hebrew Grammarian (1955); H. Malter, Saadia Gaon: His Life and Works (1926, repr. 1969); I. Efros, Studies in Medieval Jewish Philosophy (1974).