The Jewish philosopher and mutakallim (Ar. theologian, lit. discussant [of religious questions]) Abū ʾl-Khayr Dāʾūd ibn Mūsaj (also known as Abū ʾl-Khayr Dāwūd ibn Mushaj, David ben Mūsaj, Abū ʾl-Khayr al-Yahūdī, Abū ʾl-Khayr ben Yaʿīsh, and possibly Abū ʾl-Ḥusayn David ben Mashiaḥ), lived in Baghdad during the second half of the tenth century and thus was a contemporary of the Arab historian and geographer al-Masʿūdī (d. 957). It is not clear whether he was of Rabbanite or Karaite background. Abū ʾl-Khayr was once wrongly identified with the philosopher of Jewish origin Ibn al-Muqamm…