The British Museum manuscript Or. 8613 (146 folios, probably 5th–11th century) has lost both its beginning and end. Its subject is the doctrine of the Mu'tazila and it is divided into sections each of which begins with the quotation from a book by Abū 'Alī Muḥammad b. Khallād (Fihrist 174); in one place he is called ṣāḥib al-kitāb. The authorities mostly quoted are the two shaikhs, Abū 'Ahī al-Jubbāī and his son Abū Hāshim, the chief judge 'Abd al-jabbār (†415/1024) and Abū Rashīd Sa'īd b. Muḥammad who died somewhat later. He is the latest authority quoted. It is hard to decide to which of the two men Abū 'Alī refers. The MS. has been collated within the last 200 years but no other copy seems to be recorded unless no. 589 in Landberg (MSS. belonging to Maison Brill), Ziyādāt, by Abū Ṭālib Yaḥyā b. Ḥusain to al-uṣūl of Ibn Khallād, is the same work; but if the description ‘giving much information about the Zaidis’ is right, it is another book. The character of the book will be shown by a summary of its contents followed by an abridged translation of one section.