(Mecca c.600- Kufa 661) Fourth Caliph (656- 661), and the last Caliph that both Sunnis and Shi'is agree upon as justifiably elected, yet the Kharijis did not accept him from 658 and onwards. Ali was both Muhammad's cousin, being the son of Abu Talib, as well as his son-in-law by being married to Fatima. In Shi'i Islam, Ali is counted as the first Imam, a position he held from 632 when Muhammad died.
There are two dominating versions of Ali, the one of the Sunnis and the other of the Shi'is. Though both version have a positive view of him, and at least of his legitimacy of the position as Caliph, the Sunnis present him as a relatively weak ruler with many faults, while the Shi'is reject this view, and regard him infallible and the possessor of a divine light passed on from Muhammad to him, and later from him on to the other Imams.
li is believed to have been either the first or second male to convert to Islam, and he was a very devoted Muslim. Ali had several wives, and among them was Fatima, with whom he had several children, but it is Hassan and Husayn that had importance to the development of Islam.
A With the death of Muhammad in 632, the Muslim community was for a short period without a leader, and without clear indications on how to chose the new leader. Some traditions of this period tell that Muhammad had chosen Ali to be the leader, a choice not unlikely, but this is a question that have been disputed up through history. Anyway, Abu Bakr was chosen the 'deputy of the messenger', 'khalifatu r-rasuul', 'Caliph'. Ali accepted the choice, but experienced that there were forces stronger than his two more times, in 634 and 644, so he did not manage to become Caliph then either.
After the assassination of the third Caliph, Uthman, it was Ali's turn. All through his ruling period, Ali had to face strong opposition. First he was opposed by A'isha, Muhammad's favourite wife, but the strongest opposition was represented by Mu'awiyya from the Ummawiyy- family based in Syria. Mu'awiyya accused Ali for not having charged the murderers of Uthman, who was the kinsman of Mu'awiyya.
In 658 Ali gave in to some of Mu'awiyya's demands, and put down an investigation committee. This compromise was the sparkle that lead the group called Kharijis, to break with Ali. When Ali was murdered in 661, this was probably the act of a member of the Khariji sect.
The murder of Ali represents a watershed in the understanding of history among not only Shi'is, but also among Sunnis. Ali was the last Caliph coming from the group of Muslims that had converted before the hijra (622), and he was also the last elected Caliph, while the Caliphate after this became hereditary, without the nominal legitimacy. For most groups of Shi'is, the hope of a just ruling elite inside Islam, i.e. a just Islam on earth, dispersed after this. The Shi'is never accepted Mu'awiyya nor any later Caliphs, and took the name 'ash- shi^catu ^calii', 'Ali's Party', or 'Ali's followers'.