The question of the imamate or the caliphate, the designation of the Muslim community’s legitimate leader, is undoubtedly one of the most important in Islamic history. The first civil war (656-61), which broke out with the murder of Caliph `Uthman, had a profound effect not only on subsequent Islamic political and religious institutions, but also on later Muslims’ views, accounts, and discussions of the community’s early history. This bitter conflict, which necessarily involved extensive controversy concerning the identity and required qualifications of the community’s legitimate leader, laid the foundations for an enduring theological split among Islam’s three major “sects”: the Shi`ites, the Sunnis, and the Kharijis – one that would persist long after the war ended with the assassination of `Ali.
Polemics among these groups, and among subcategories of the three main groups, each of which endeavored to justify its contemporary views on legitimate leadership and sectarian identity, were a creative force in many fields. Bodies of theoretical discussion, primarily in theology but also in law and other fields, grew around these polemics, using prooftexts from the Qur’an and Hadith, as well as historical accounts, as evidence in arguments about the Companions, their relationships with the Prophet, their relative merits and other moral qualities, and their dealings with each other. Though focused on a much earlier period and concerning conflicts long over, these polemics were all the more sensitive and emotionally charged because of their contemporary implications concerning the legitimacy of the sectarian groups’ beliefs.