Shi'a Islam (also called Shiite, or Shi'i) is the second largest division of Islam, constituting about 10-15% of all Muslims. The Sunni Muslims recognise the Four Caliphs as 'rightly guided', while Shi'a Muslims recognise Ali as the First Caliph and his descendants. Shi'as differ on how many Imams there have been. Some talk of Twelve and others of Fourteen. They also differ on who is the last Imam (Mahdi). Imamites say it was the Twelfth Imam, Muhammad al'Mahdi, the Zaydites say the Fifth, Zayd, and, the Isma'ilites say the Seventh Imam, Ismail. However, Shi'as agree that the Last Imam went into hiding and will return to bring in the end of the world.
The five Shia principles of religion (usul ad din) are: belief in divide unity (tawhid); prophecy (nubuwwah); resurrection (maad); divine justice (adl); and the belief in the Imams as successors of the Prophet (imamah). The latter principle is not accepted by Sunnis.
Most Sunnis believe the Sharia (religious law of Islam) was codified and closed by the 10th century. Shia followers believe the Sharia is always open, subject to fresh reformulations of Sunna, hadith, (traditions of what Muhammad and his companions said and did) and Qur'an interpretations.
Like Sunni Islam, Shia Islam has developed several sects. Because of their belief that the leader of the Muslim community must be a blood relative of the prophet, disputes arose when two sons of an Imam (the title given to the Shia leader) both claimed to be the rightful successor. These disputes caused the Shia sect to further divide into three groups: Zaids, Ismai'ilis, and Ithna Asharis. The Twelver or Ithna-Ashari sect is the most important of these, as it predominates not only in Iraq but in the Shia world generally. Broadly speaking, the Twelvers are considered political quietists as opposed to the Zaydis who favor political activism, and the Ismailis who are identified with esoteric and gnostic religious doctrines.
Canonical schools in Islam, are called "Fiqh's"; the only Fiqh's in Shia Islam, are Usuli, Akhbari, and Shaykhi. These 3 all belong to the Ithna-Ashari or mainstream Shia Islam, which believes in the 12 Shia Imams; hence the name which means "Twelver's". The dominant Shia legal school is sometimes termed the Ja'fari Fiqh, after lmam Jaafar Sadiq (a.s.), the Sixth Infallible Imam of the world of Shiism. The term "Jaafari" is something of a pejorative term, just like "Wahhabiyyah" is; and one that is not used by Shias themselves. It is used by Sunnis, to derided Shias, just as "Wahhabiyyah" is used by Westerners and Shias, to deride Sunnis, but neither term is correct in and of itself.
A student assimilates from very early the ijtihad methodology as he assumes religious ranks: preacher, then mujtahid, hujjat Al-Islam [Proof of Islam], and then hujjat Al-Islam wa Al-Muslimeen until he becomes a Source or ayatollah, and thereafter the great ayatollah or ayatollah al-`uzma.
The 1964 Afghan Constitution, which was the basis of new 2003 constitution, stated: "Islam is the sacred religion of Afghanistan. Religious rites performed by the state shall be according to the provisions of the Hanafi school of jurisprudence." This stipulation left Afghan Shia without proper representation. Thus in March 2003, Ayatollah Mohammad Asef Mohseni, leader of the predominantly Shia Harakat-e Islami-yi Afghanistan, proposed that, along with the Sunni Hanafi school of jurisprudence, the Shia Ja'fari school of jurisprudence be included in the new constitution as an official sect. Mohseni said he proposed two additional formulas if his proposal is not accepted: mentioning "Islam and the Islamic sects," or just mentioning Islam without any mention of sects to ensure that Afghan Shia have their jurisprudence recognized and are allowed to "perform their religious duties according to it."
The Ja'fari [Hafari] fiqh of the Imami Shias is in most cases indistinguishable from one or more of the four Sunni madhahib, except that "Muta'h" or temporary marriage is considered lawful by the Fiqh Jafari, whereas it is prohibited in all the Sunni schools. But the Shia are still viewed with great caution by the Ulema of the Sunni world. Although Sunni and Shi'a Muslims are historically ambivalent, this traditional enmity was dampened in Central Asia due to shared resistance to Russian and Soviet rule. Indeed, both Sunni and Shi'a delegations to the 1905 Third Congress of Muslims in Russia declared Ja'farite Shi'ism as a fifth legal school, equivalent to the Hanafi, Maliki, Hanbali, and Shafi'i madrasehs.
Shi'as do not believe in predestination. They accept the teachings of the Mu'tazilities, a group of Sunni scholars who were later declared heretical. The Mu'tazilities believed that God cannot be responsible for evil, and therefore, humans must have freewill and be independent of God's authority in this life. A further belief of Shia Muslims concerns divine justice and the individual's responsibility for his acts, which are judged by a just God. This contrasts with the Sunni view that God's creation of man allows minimal possibility for the exercise of free will.
Two distinctive and frequently misunderstood Shia practices are mutah, temporary marriage, and taqiyah, religious dissimulation.
Mutah, that is, marriage with a fixed termination contract subject to renewal, was practiced by Muslims as early as the formation of the first Muslim community at Medina. Banned by the second caliph, it has since been unacceptable to Sunnis, but Shias insist that if it were against Islamic law it would not have been practiced in early Islam. Mutah differs from permanent marriage because it does not require divorce proceedings for termination because the contractual parties have agreed on its span, which can be as short as an evening or as long as a lifetime. By making the mutah, a couple places the sexual act within the context of sharia; the act then is not considered adulterous and offspring are considered legitimate heirs of the man.
Taqiyah is another practice condemned by the Sunni as cowardly and irreligious but encouraged by Shia Islam and also practiced by Alawis and Ismailis. A person resorts to taqiyah when he either hides his religion or disavows certain religious practices to escape danger from opponents of his beliefs. Taqiyah can also be practiced when not to do so would bring danger to the honor of the female members of a household or when a man could be made destitute as a result of his beliefs. Because of the persecution frequently experienced by Shia imams, particularly during the period of the Umayyad and Abbasid caliphates, taqiyah has been continually reinforced.
Shia practice differs from that of the Sunnis concerning both 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.