The most popular school of thought in Islam.
Ja'fari. The Ja'fari school of thought was headed by Imam Ja'far ibn Muhammad al-Sadiq ( pbuh ) who lived from 83 h . to 148 h . He was born in and died in the holy city of Madinah and is the sixth imam of the twelve designated imams of the school of ahl al-bayt . Although the fiqh (Islamic jurisprudence) was developed by the Holy Prophet Muhammad ( pbuh&hf ) and his successors (the imams ), the fiqh as taught by the Shi'a did not have the opportunity to be presented to the masses because of the political predicament that the ahl al-bayt suffered from under the rulers for many centuries. Because they refused to acknowledge the legitimacy of the Umayyid and 'Abbasid caliphs and their governments, the imams of the ahl al-bayt and their followers were exposed to tremendous harassment and persecution at the hands of the caliphs. Once the Umayyid government became weak, Imam Ja'far ibn Muhammad al-Sadiq ( pbuh ) found a golden opportunity to formulate and spread the tradition of the Holy Prophet Muhammad ( pbuh&hf ) and his family ( pbut ). At one time, four thousand scholars, Qur'anic commentators, historians, and philosophers attended his classes in the holy city of Madinah. Therefore, he was able to pass down the authentic teachings of the Holy Qur'an and the Holy Prophet Muhammad ( pbuh&hf ) and crystallize them in what came to be known as al-fiqh al-ja'fari , the Ja'fari jurisprudence. His teachings were collected in 400 usul (foundations) which were written by his students and encompass hadith , Islamic philosophy, theology, Qur'anic commentary, literature, and ethics.