Sixth Shii imam. The dispute over which son was to succeed him led to the split between the Twelver (Ithna Ashari) Shiis and the Sevener (Ismaili) Shiis. He founded the Jafari school of Islamic law, the most important in Shiism. Taught that the true caliph and ruler of the Muslim community had to be a descendant of Ali, designated by his predecessor to inherit secret knowledge and the exclusive authority to interpret the Quran and hadith, and to elaborate the legal system. He shifted the emphasis of Shiism from political issues to religious teachings and highlighted the sacred origins of craft corporations. Patron saint of the Bektashi Sufi order.