Hezbollah boy scouts carry a poster of the late Ayatollah Ruhollah Khomeini, the father of the Islamic Revolution in Iran, during a march to mark Ashura in the suburbs of Beirut, Lebanon, Tuesday Jan. 30, 2007. On Ashura, Shia commemorate the death of Imam Hussein, grandson of the Prophet Muhammad, who was beheaded in Karbala, Iraq in 680 A.D. in a battle about who was to succeed Muhammad. (AP Photo/Hussein Malla)

Both Sunni and Shia Muslims share the fundamental Islamic beliefs and articles of faith. The schism between the two initially stemmed not from spiritual differences but from political ones. After the death of the Prophet Muhammad, a debate ensued over who should take his place as leader of the faith. Most of the prominent Muslims of Medina claimed that Muhammad had named no successor and elected Abu Bakr, the Prophet’s closest advisor and companion, as the first caliph (successor). This was an extremely controversial appointment, as other Muslims argued that Muhammad had designated Ali ibn Abi Talib as his successor. Ali was the Prophet’s son-in-law and closest male relative, and those who supported him felt not only that his succession had been the intention of the Prophet but also that his blood tie to Muhammad was a sacred bond.

Other regional tribes who had accepted Islam were breaking from the faith upon Muhammad’s death, and without strong leadership the regional cohesiveness that had been established in Muhammad’s time was threatened. Perhaps with that in mind, Ali neither supported nor actively opposed the election of Abu Bakr, who reigned briefly as caliph and effectively suppressed the various uprisings.

Ali’s supporters, who believed that direct descendants of Muhammad were the only rightful leaders of the faith, would become known as the Shia (from “Shi’at Ali,” or “the party of Ali”). Those who became the Sunni believed instead that their leaders should be elected from among those most capable of worldly as well as spiritual leadership. Both sides occasionally gained control in the fractious early Caliphate, and although Ali eventually became the fourth caliph, his reign was short and ended in assassination. He was followed by Muawiyah of the prominent Umayyad family, but when Muawiyah was succeeded by his son, Yazid I, the Shia revolted, demanding that Ali’s son, Hussein, be named caliph. Hussein set out from Mecca to meet his supporters, but he and his family were massacred by Umayyad troops at the Battle of Karbala. While political power would occasionally still shift after this, the Shia were to remain an often-persecuted minority throughout the era of the Caliphate.

Shia doctrine is based on an esoteric interpretation of Islam established by the “imams,” religious leaders who were descendants of Muhammad and whom the Shia consider to be the sole interpreters of Islamic theology. In Shiism, the Qur’an contains layers of meaning beneath the literal meanings that were revealed by the imams. The Shia also have their own versions of the “hadith,” the collected sayings and deeds of the Prophet, and thus have a distinct interpretation of Islamic law and culture. The Shia tradition adds to Islam a significant passion element, the observance of the murders of Ali and Hussein, and an occult and messianic element, the belief that Muhammad al-Mahdi, the twelfth and “hidden” imam who disappeared in 874 A.D., is alive but hidden from the world by God and will return in the final days to restore the world to justice. Politically, generations spent as a persecuted minority have made the Shia quicker to resent authority than the Sunni and to view spiritual life as a struggle for social justice and against oppression.

While the Shia certainly remain a minority denomination, their practices and beliefs have had a broad impact on the larger Islamic world.