First of the Jewish medieval philosophers. His fight against the Karaite sect, which broke away from traditional Judaism, was decisive in preserving the unity of historical Jewry. He was born at Fayyum, Egypt. At 20, he compiled a Hebrew dictionary. He also translated the Bible into Arabic and wrote a commentary on most of its books. At about the same time, he combated the Karaite attack on the Talmud, refuting all the arguments of their leader, Anan Ben David. Saadiah’s brilliant defense of the Talmud spread his fame throughout the Jewish world. Saadiah left Egypt and spent some years in Palestine. At that time, Babylonia was still a great center of Jewish learning. The head of the Academy of Palestine, Ben Meir, disputed the right of the Babylonian scholars to compute the calendar. Saadiah sided with the Babylonian academies, and strengthened their authority.

When he arrived in Babylonia, he was invited to become head of the ancient Academy of Sura. Saadiah accepted the post, revitalized the Academy, and reestablished its fame. Unfortunately, a dispute arose between Saadiah and the exilarch, David ben Zakkai. The exilarch succeeded in bribing the Caliph to side with him, and the Gaon was forced to hide in Baghdad for seven years. During his forced exile, he produced his most important work, written in Arabic and called Beliefs and Opinions. His aim was to prove that the Jewish religion is based on reason and does not contradict philosophic thought. The book exerted great influence on Jewish thought, and is one of the standard works of Jewish religious philosophy. Five years before his death, Saadiah was reinstated as head of the Academy of Sura.