Just as for all Muslims Islam has always existed because it is the one eternal truth, from a Shiite point of view, Shiism is nothing else than this eternal truth and begins with the creation of mankind. According to various strands within the Shiite tradition, the key figures of Shiite salvation history accepted their future fate in the material world before human history, and thus Shiite history began at that point. Yet, for historians who seek to identify a set of distinctive features that characterize the way Shiites define themselves and are defined by others, answers to the questions about when Shiism began and what it is are not straightforward.
One problem in the historiography of Shiism is that later divisions and features are often projected back into the early days of Islam. The rift between Sunnis and Shiites may have its origins in the divisions over the succession of Muhammad, but the two groups took several centuries to develop into separate and distinct sects. This concerns especially Sunnism, which crystallized as a branch of—rather than simply mainstream—Islam in contrast to Shiism. While the latter had been visible much earlier on, some features of Shiism as it exists or is commonly perceived today—such as the clergy in Iran—are only very recent developments of modernity. At the same time, some features that are commonly identified with Shiism, such as the superior religious authority of the political leader, once applied to the entire Muslim community.
Until the publication of Patricia Crone and Martin Hinds' God's Caliph(2003), which presents ample evidence for such claims in the Umayyad period, it was assumed that most early Muslims saw the caliph only as a political leader and that the "Shiite" way of combining political and religious authority was "deviant." Similar notions appear in phenomenological observations concerning controversial religious practices of Sunnis. Visiting the tombs of distinguished Muslims thus becomes a "typically Shiite" activity and messianic claims of political leaders a "typically Shiite" form of authority. This points to the more general difficulty issuing from the misperception that the minority status of Shiites within Islam may suggest that Shiism is less authentic than Sunnism. The same applies to the label 'sect,' which could incorrectly be understood to suggest that Shiites split off from Sunnism.
The anachronistic use of concepts is a hermeneutical problem in any historical question, but it is particularly difficult to avoid in cases where contemporary sources are as scarce as in early Islamic history. The earliest preserved accounts of the First Civil War only stem from a period when sectarian divisions were already established. The earliest written Shiite sources date to the 8th century and were written by Kufan supporters of the Alids, but apart from their titles nothing is preserved. Given that the attitudes of Shiites to the first three caliphs changed and that key doctrinal notions were only developed in the 9th century, it is likely that the way Shiites told the history of their own origins underwent a process of reinterpretation and harmonization.
While the origins of Shiism may lie in Muhammad's death, for its development as a distinctive branch or sect within Islam and mutually exclusive with other branches it is necessary to consider what is usually labeled the formative period of Islam, i.e., the second and third centuries of its history. It was only then that the crucial concept of the Imam was developed and that political and religious aspects of Shiism were combined in a more coherent and elaborate form.
The later part of this period is marked by internal disagreements among the Shiites not unlike the conflicts following Muhammad's death. Shiites disagreed over the line of succession of the Imams, but following the death of the eleventh Imam, Hasan al-Askari in 874, opinions also varied concerning the nature of the Imam and whether he was part of this world or removed in an upper sphere. As in studies of the emergence of Islam, modern historians have to rely on later documents, which often reflect negotiated narratives or interpretations imposed by the most powerful fraction. This is the case, for example, with the Fatimids who presented themselves as the only true Ismailis and other representatives of this branch of Shiism as having left this path.