The volume contains critical editions of the extant parts of two hitherto unknown theological works by the Būyid vizier al-Ṣāḥib b. ʿAbbād (d. 385/925), who is well known to have vigorously promoted the teaching of Muʿtazilī theology throughout Būyid territories and beyond. The manuscripts on which the edition is based come from Cairo Geniza store rooms. They consist of two manuscripts for each of the two texts—testimony to the impact of al-Ṣāḥib’s education policy on the contemporaneous Jewish community in Cairo. The longer treatise of al-Ṣāḥib of ca. 350/960, possibly his Kitāb Nahj al-sabīl fī uṣūl al-dīn, appears to be the earliest Muʿtazilī work preserved among the Jewish community. The second, briefer treatise also contains a commentary by ʿAbd al-Jabbār al-Hamadānī (d. 415/1025).