He studied under al-Zajjāj, Ibn Durayd, and a number of other authorities. Among those who narrated from him were Abū al-Qāsim al-Tanūkhī, al-Jawharī, and Hilāl ibn al-Muḥassin.
He authored works on QurꜤānic exegesis, philology, grammar, and speculative theology (kalām). He composed commentaries on Sībawayh’s Kitāb and on the book al-Jumal, and produced treatises on derivation, morphology, and other subjects. In Muʿtazilī doctrine he wrote Ṣanʿat al-Istidlāl in seven volumes, the Book of Names and Attributes, the Book of Created Entities, and the Book of the Known and the Unknown. In all, his output approached one hundred titles.
He inclined toward Shiʿism and asserted, “ʿAlī is the most excellent of the Companions.”(1)
Abū Ḥayyān al-Tawḥīdī went to great lengths in exalting al-Rummānī, describing him as god-fearing, ascetic, eloquent, and devout.
He died in Jumādā al-Ūlā 384 AH, at the age of eighty-two. His roots lay in Sāmarrāʾ, yet he passed away in Baghdad, and he was counted among the great vessels of learning despite his innovation.