'ALĪ, IBN ABĪ TĀLIB. – Cousin and son-in-law of Muḥammad, and his fourth successor as head of the Muslim community; the last in the series of the “orthodox” or “rightly guided” caliphs (Rāfidān). Son of a brother of Muḥammad’s father, he was considerably younger than the prophet. He was among the first to embrace Islām, and his ties of kinship with Muḥammad were strengthened when he married his daughter Fāṭimah, by whom he had the two sons al-Ḥasan and al-Ḥusain, progenitors of all the subsequent, real or supposed, descendants of the Prophet.
'A. faithfully assisted his cousin during the difficult first years of the Meccan preaching, followed him to Medina in the hijra, and distinguished himself for martial valor in the battles and military expeditions of the first decade. It does not seem, however, despite the assertions of tendentious Shiite tradition, that he enjoyed special influence with the prophet, perhaps because of his limited political sense and his temperament, courageous in the field but irresolute. Under the rule of the third caliph 'Oṭmān, 'A. became the leader of the opposition, which was composed of pietistic elements (the so-called Qurrā', “readers,” or reciters of the Qur’an), Medinan Muslims hostile to the long-pagan family of the Omajjads, to which 'Oṭmān himself belonged, and agitators and rebels. In the disturbances that culminated in the murder of 'Oṭmān in 656, 'A. played an unclear role that morally compromised him in the eyes of the opposing Omajjad party, since he benefited from the caliph’s assassination by succeeding him.
As soon as he came to power, he therefore encountered the opposition of other former companions of the prophet, such as Ṭalḥa and az-Zubair, supported by Muḥammad’s widow, 'Ā'īšah. Victorious over them in the so-called Battle of the Camel (November 656), 'A. had to face a far more serious danger in the resurgence of the Omajjad party, led by the governor of Syria, Mu'āwijah ibn Abi-Sufjān, and risen under the slogan “vengeance for 'Oṭmān.” When attempts at settlement proved fruitless, 'A. also marched against Mu'āwijah and engaged his army at Ṣiffīn on the right bank of the middle Euphrates. But the battle, whose outcome was appearing favorable to 'A., was suspended through the skillful appeal of Mu'āwijah’s supporters for arbitration “according to the Qur’an” (as they expressed it in an equivocal formula). His political career was obstructed and finally cut short by the fanatical movement of the Ḥāṅgīti, whom he defeated at the battle of Nāhrawān, without, however, succeeding in eradicating their movement, which for approximately a century was to constitute a source of bloody rebellions and disturbances within the Islamic community.
'A., from whom his adversary Mu'āwijah had wrested Syria and Egypt, fell victim in January 661 to a ḥāṅgīta attack in the mosque of Kūfa, which he had made his capital from the time of his accession. Mu'āwijah was universally recognized as caliph and initiated the dynasty of the Omajjads, while 'A.’s descendants, and first of all his two sons, were left with only the choice between renouncing every political aspiration (as the elder, al-Ḥasan, did), or conspiracy and sterile insurrection, bloodily repressed, as was the fate, twenty years later, of the younger son, al-Ḥusain.
Entirely disproportionate to 'A.’s historical career, to his mediocre character, and to the failure of his life is the importance that his figure assumed in the subsequent development of the Muslim religion. Regarded by the Sunnites or orthodox as the wise and valiant right arm of the prophet, he was held by the Shiites to be his sole legitimate heir, both in the direction of the Islamic community and in the very prerogatives of prophetic inspiration and infallibility. This conception then culminated, among the currents of the extreme Shi'a, in the actual deification of 'A., placed above Muḥammad himself and regarded as the supreme incarnation on earth of the divine logos. It may be said that, apart from the Hāriqīti, by then almost entirely extinct, all heterodox Islām moved within the orbit of veneration for 'A. and of the transformation of his historical figure. Even for the Christian West, he became known at once alongside Muḥammad; and Dante placed 'A. (the accentuation, which does not correspond to the Arabic form of the name, is due to the influence of Turkish pronunciation) among the sowers of scandal and schism, with an obscure awareness of the complications within Islam itself that converge upon this disconcerting and tragic figure.