Al-Shahrastānī (d. A.H. 548 / C.E. 1153) was an influential historian of religions and a heresiographer. He was one of the pioneers in developing a scientific approach to the study of religions. Al-Shahrastānī’ distinguished himself by his desire to describe in the most objective way the universal religious history of humanity. He was wrongly recognized as an “Ash‘arite” theologian; this is why some scholars such as Muhammad Ridā Jalālī Nā’īnī, Muhammad Taqī Dānish-Pazhūh, Wilferd Madelung, Jean Jolivet, and Guy Monnot firmly believe that he was an Ismā‘īlī who was practicing taqiyya (religious dissimulation) since Ismā‘īlis were persecuted during that time. Very few things are known about al-Shahrastānī’s life. He was born in A.H. 479/ C.E. 1086 in the town of Shahristān (Republic of Turkmenistan) where he acquired his early traditional education. Later, he was sent to Nīshāpūr where he studied under different masters who were all disciples of the Ash‘arite theologian al-Juwaynī (d. A.H. 478 / C.E. 1085). At the age of 30, al-Shahrastānī went to Baghdad to pursue theological studies and taught for three years at the prestigious Ash‘arite school, the Nizāmiyya. Afterwards, he returned to Persia where he worked as Nā’ib (Deputy) of the chancellery for Sanjar, the Saljūq ruler of Khurāsān. At the end of his life, al-Shahrastānī went back to live in his native town.