The fundamental distinction between Sunni and Shiite Islam involves differences of opinion regarding the rightful heir to the Prophet Muhammad, who advanced the cause of Islam throughout the Arabian Peninsula during the early 7th Century. Disagreements, which provided the basis for the schism between the two sects that survives to this day, revolve around the belief of Sunni Muslims that the rightful successor, or Caliph, should be selected upon the basis of qualifications versus the Shiite Muslim belief that the succession process should evolve along familial lines. The first successor, or Caliph, on which both sides initially agreed, at least a temporary solution, was Abu Bakr, one of the deceased Muhammad's closest followers. Consensus, however, broke down almost immediately, as those who would become categorized as Shi'a, or Shiite, continued to agitate on behalf of Ali ibn Abi Talib, Muhammad's cousin and son-in-law, who was married to the late prophet's daughter. The phrase or designation "Shi'a" refers to followers of Ali. The Sunni sect emerged out of the continued opposition to designating Muhammad's successor on the basis of hereditary factors or family relationships. Sunni Muslims, who comprise the vast majority of Muslims worldwide, continue to believe that the rightful successor to Muhammad should be determined on the basis of fealty to the Prophet's customs, or sunna.
The schism between Sunni and Shiite Muslims continues because of the deep commitment on both sides to the notion of selecting the truest or purist follower of Muhammad's ways.
- Shiites did not agree on the elected Caliphs. They believe they should only be descendants of Muhammad.
- Sunnis are considered the orthodox version of Islam.
- There are more Sunnis than Shiites.