SHAHRASTĀNĪ, AL- (1086–1153), more fully, Abū al-Fath Muḥammad ibn ʿAbd al-Karīm al-Shahrastānī, was a Muslim theologian, heresiographer, and historian of religions. His extant biographical profile, derived from the thirteenth-century biographical dictionary of Ibn Khallikān, remains thin. He was born in 1086 in the town of Shahrastan in Khorasan (Iran). There he obtained his earliest education, studying both jurisprudence (fiqh) and theology (kalām) under accepted masters. He aligned himself with the dominant Ashʿārī school of kalām, although his independent intellect led him to declare the shortcomings as well as the benefits of al-Ashʿārī's system.

The formative period in his life began at age thirty. On his return from the pilgrimage to Mecca, he stopped in Baghdad for three years to pursue further theological studies. His presence was forceful: By his interaction...