At the time of Prophet Muhammad, the terms “Sunni” and “Shi’ah” did not exist — they developed later in Muslim history. After the Prophet passed away, Muslims were left to determine who should rightfully succeed him as the political leader (khalifah) of the Muslim community. Many were of the belief that a leader could be selected among any of the righteous and pious Muslims who demonstrated leadership abilities. This has come to be known as the majority viewpoint, designated “Sunni” in reference to these Muslims’ reliance on the Qur’an and Sunnah of Muhammad as the sources of religious doctrine and practice.
Others believed that the position had been conferred upon Ali ibn Abu Talib, cousin and son-in-law of Muhammad, by the Prophet. In the ensuing years, this difference of opinion was perpetuated, as the Shi’ah (“supporters” or “partisans” of Ali) continued to hold that authority belonged to Ali and his immediate descendants, even while historically, leadership was exercised by various dynasties such as those of the Umayyads and Abbasids.
Ali and eleven successive descendants are given the title Imam by Shi’ahs and they are considered the rightful, designated successors of Prophet Muhammad. The Arabic term “imam” literally means “leader” or “model,” and is commonly used to refer to the leader of formal congregational worship. Shi’ah Muslims use the term more reverentially, since the Imams are believed to be sinless and to have knowledge of things unknown to others. Furthermore, the teachings of the Imams are given weight similar to that of the Qur’an and Sunnah as a source for correct belief and practice.
Shi’ahs also believe that the twelfth and final Imam, born in 868 C.E., continues to live, albeit in a miraculous state of occultation (concealment from human view). The Hidden Imam is believed to enact God’s plan in the world and provide continued guidance on behalf of the first Imam Ali.