The Imāmī scholar Abū Jaʿfar Ṭūsī (d. 459-60/1066-7) was born in Ṭūs in Khurāsān. Having completed his basic education there, he left for Baghdad, which at the time was ruled by the Shīʿī Buwayhid dynasty. In Baghdad he attended the classes of various prominent scholars, notably the leading Imāmī rationalist of his time, al-Shaykh al-Mufīd (d. 413/1022) and his successor al-Sharīf al-Murtaḍā (d. 436/1044). After the death of al-Murtaḍā, Ṭūsī, who had already made a name for himself as a thinker and a writer, became the undisputed leader of the Imāmī community. About ten years later Baghdad was invaded by the Saljuqs and Ṭūsī’s house and libraries were laid to waste. Tūsī fled to Najaf where he remained until his death. Al-Muqaddima fi ʼl-kalām on concepts in theology figures among Ṭūsī’s most important works. The commentary by Najīb al-Dīn al-Ḥusaynī (d. 582/1186) printed in facsimile here are lecture notes, made by one of his students.