Shia Muslims hold the fundamental beliefs of other Muslims (see Sunni Islam , this ch.). In addition to these tenets, however, Shia believe in the imamate, which is the distinctive institution of Shia Islam. Whereas Sunni Muslims view the caliph as a temporal leader only and consider an imam to be a prayer leader, Shia Muslims hold a hereditary view of Muslim leadership. They believe the Prophet Muhammad designated Ali to be his successor as Imam (when uppercase, Imam refers to the Shia descendant of the House of Ali), exercising both spiritual and temporal leadership. Only those who have walayat (spiritual guidance) are free from error and sin and have been chosen by God through the Prophet. Each Imam in turn designated his successor--through twelve Imams--each holding the same powers.

The imamate began with Ali, who is also accepted by Sunni Muslims as the fourth of the "rightly guided caliphs" to succeed the Prophet. Shia revere Ali as the First Imam, and his descendants, beginning with his sons Hasan and Husayn, continue the line of the Imams until the twelfth. Shia point to the close lifetime association of the Prophet with Ali. When Ali was six years old, he was invited by the Prophet to live with him, and Shia believe Ali was the first person to make the declaration of faith in Islam. Ali also slept in the Prophet's bed on the night of the hijra, when it was feared that the house would be attacked by unbelievers and the Prophet stabbed to death. He fought in all the battles the Prophet did, except one, and the Prophet chose him to be the husband of one of his favorite daughters, Fatima.

Among Shia, the term imam traditionally has been used only for Ali and his eleven descendants. None of the twelve Imams, with the exception of Ali, ever ruled an Islamic government. During their lifetimes, their followers hoped that they would assume the rulership of the Islamic community, a rule that was believed to have been wrongfully usurped. Because Sunni caliphs were cognizant of this hope, Imams generally were persecuted under the Umayyad and Abbasid dynasties. Therefore, the Imams tried to be as unobtrusive as possible and to live as far as was reasonable from the successive capitals of the Islamic empire.

During the eighth century, Caliph Al Mamun, son and successor to Harun ar Rashid, was favorably disposed toward the descendants of Ali and their followers. He invited Imam Reza, the Eighth Imam (765-816), to come from Medina to his court at Marv (Mary in present-day Turkmenistan). While Reza was residing at Marv, Al Mamun designated him as his successor in an apparent effort to avoid conflict among Muslims. Reza's sister, Fatima, journeyed from Medina to be with her brother but took ill and died at Qom, in present-day Iran. A major shrine developed around her tomb, and over the centuries Qom has become a major Shia pilgrimage site and theological center.

Al Mamun took Reza on his military campaign to retake Baghdad from political rivals. On this trip, Reza died unexpectedly in Khorasan. Reza was the only 1930 y Imam to reside in, or die in, what is now Iran. A major shrine, and eventually the city of Mashhad, grew up around his tomb, which is the major pilgrimage center in Iran. Several theological schools are located in Mashhad, associated with the shrine of the Eighth Imam.

Reza's sudden death was a shock to his followers, many of whom believed that Al Mamun, out of jealousy for Reza's increasing popularity, had the Imam poisoned. Al Mamun's suspected treachery against Imam Reza and his family tended to reinforce a feeling already prevalent among his followers that Sunni rulers were untrustworthy.

The Twelfth Imam is believed to have been only five years old when he became Imam in 874 on the death of his father. Because his followers feared he might be assassinated, the Twelfth Imam was hidden from public view and was seen only by a few of his closest deputies. Sunnis claim that he never existed, or that he died while still a child. Shia believe that the Twelfth Imam never died, but disappeared in about 939. Since then, the greater occultation of the Twelfth Imam has been in force, which will last until God commands the Twelfth Imam to manifest himself on earth again as the mahdi or messiah. Shia believe that during the occultation of the Twelfth Imam, he is spiritually present--some believe that he is materially present as well--and he is besought to reappear in various invocations and prayers. His name is mentioned in wedding invitations, and his birthday is one of the most jubilant of all Shia religious observances.

The Shia doctrine of the imamate was not fully elaborated until the tenth century. Other dogmas developed still later. A characteristic of Shia Islam is the continual exposition and reinterpretation of doctrine.

A significant practice of Shia Islam is that of visiting the shrines of Imams in Iraq and in Iran. In Iraq, these include the tomb of Imam Ali in An Najaf and that of his son, Imam Husayn, in Karbala, because both are considered major Shia martyrs. Before the Iran-Iraq War (1980-88), tens of thousands made the visits each year. Other principal pilgrimage sites in Iraq are the tombs of the Seventh Imam and the Ninth Imam at Kazimayn near Baghdad. In Iran, pilgrimage sites include the tomb of the Eighth Imam in Mashhad and that of his sister in Qom. Such pilgrimages originated in part from the difficulty and the expense of making the hajj to Mecca in the early days.

In commemoration of the martyrdom of Husayn, killed near Karbala in 680 during a battle with troops supporting the Umayyad caliph, processions are held in the Shia towns and villages of southern Iraq on the tenth day of Muharram (Ashura), the anniversary of his death. Ritual mourning (taaziya) is performed by groups of five to twenty men each. Contributions are solicited in the community to pay transportation for a local group to go to Karbala for taaziya celebrations forty days after Ashura. There is great rivalry among groups for the best performance of the taaziya passion plays.

Shia practice differs from Sunni practice concerning divorce and inheritance in that it is more favorable to women. The reason for this reputedly is the high esteem in which Fatima, the wife of Ali and the daughter of the Prophet, was held.

Like Sunni Islam, Shia Islam has developed several sects. The most important of these is the Twelver, or Ithna-Ashari, sect, which predominates in the Shia world generally. Not all Shia became Twelvers, however. In the eighth century, a dispute arose over who should lead the Shia community after the death of the Sixth Imam, Jaafar ibn Muhammad (also known as Jaafar as Sadiq). The group that eventually became the Twelvers followed the teaching of Musa al Kazim another group followed the teachings of Musa's brother, Ismail, and were called Ismailis. Ismailis are also referred to as Seveners because they broke off from the Shia community over a disagreement concerning the Seventh Imam. Ismailis do not believe that any of their Imams have disappeared from the world in order to return later. Rather, they have followed a continuous line of leaders represented in early 1993 by Karim al Husayni Agha Khan IV, an active figure in international humanitarian efforts. The Twelver Shia and the Ismailis also have their own legal schools.

Another group, the Kharijites, arose from events surrounding the assassination of Uthman, the third caliph, and the transfer of authority to the fourth caliph, Ali. In the war between Ali and Muawiyah, part of Ali's army objected to arbitration of the dispute. They left Ali's camp, causing other Muslims to refer to them as "kharijites" (the ones who leave). The term Kharijites also became a designation for Muslims who refused to compromise with those who differed from them. Their actions caused the Sunni community to consider them assassins.

In the eighth century, some Kharijites began to moderate their position. Leaders arose who suppressed the fanatical political element in Kharijite belief and discouraged their followers from taking up arms against Islam's official leader. Kharijite leaders emphasized instead the special benefits that Kharijites might receive from living in a small community that held high standards for personal conduct and spiritual values. One of these religious leaders, or imams, was Abd Allah ibn Ibad, whose followers founded communities in parts of Africa and southern Arabia. Some of Abd Allah's followers, known as Ibadis, became the leaders of Oman.

Data as of January 1993