The Prophet Muḥammad laid the foundations of a new religion which was propagated as the seal of the great monotheistic religions of the Abrahamic tradition. Thus, Islam from early on claimed to have completed and superseded the messages of Judaism and Christianity, whose adherents were accorded a special status among the Muslims as the ‘people of the book’ (ahl al-kitāb). However, the unified and nascent Muslim community (umma) of the Prophet's time soon divided into numerous rival groups, as Muslims disagreed on a number of fundamental issues.

Modern scholarship has indeed shown that at least during the first three centuries of their history, marking the formative period of Islam, Muslims lived in an intellectually dynamic and fluid milieu characterized by a multiplicity of communities of interpretation, schools of thought, and a diversity of views on a range of religio-political issues. The early Muslims were confronted by many puzzles relating to their religious knowledge and their understanding of Islam, which revolved around major issues such as the attributes of God, the nature of authority and definitions of believers and sinners. It was during this formative period that different groups and movements began to formulate their doctrinal positions and gradually acquired their distinctive identities and designations.