Tāj al-Dīn Abū al-Fath Muhammad ibn `Abd al-Karīm ash-Shahrastānī (Arabic: تاج الدين أبو الفتح محمد بن عبد الكريم الشهرستاني; 1086–1153 CE), also known as Muhammad al-Shahrastānī, was an influential Persian historian of religions, a historiographer, Islamic scholar, philosopher and theologian. His book, Kitab al–Milal wa al-Nihal (lit. The Book of Sects and Creeds) was one of the pioneers in developing an objective and philosophical approach to the study of religions. Source: Wikipedia (en)