Saadia Gaon
Saʿadia ben Yosef Gaon (Arabic: سعيد بن يوسف الفيومي Saʿīd bin Yūsuf al-Fayyūmi; Hebrew: סַעֲדְיָה בֶּן יוֹסֵף אַלְפַיּוּמִי גָּאוֹן Saʿăḏyā ben Yōsēf ʾal-Fayyūmī Gāʾōn; alternative English names: Rabbeinu Saʿadiah Gaon ("our Rabbi [the] Saadia Gaon"), often abbreviated RSG (RaSaG); Saadia b. Joseph; Saadia ben Joseph; Saadia ben Joseph of Faym; or Saadia ben Joseph Al-Fayyumi; 882/892 – 942) was a prominent rabbi, gaon, Jewish philosopher, and exegete who was active in the Abbasid Caliphate. Saadia is the first important rabbinic figure to write extensively in Judeo-Arabic. Known for his works on Hebrew linguistics, Halakha, and Jewish philosophy, he was a practitioner of the philosophical school known as the "Jewish Kalam". In this capacity, his philosophical work The Book of Beliefs and Opinions represents the first systematic attempt to integrate Jewish theology with components of ancient Greek philosophy. Saadia was also very active in opposition to Karaite Judaism in defense of rabbinic Judaism.