The Conceptual Evolution of the Principles of Religion (Usul al-din) in Imami Shi'a

Usul is one of the most important issues of the formative period of Imami Shi'a theology. This article tends to discuss the history of the development of the usul and its formulation in a standard set of beliefs. Their graduate emergence in a certain historical moment and evolvement in the course of history. The present study with a historical approach and an analytical method will explore the concept and terms of the usul and show that what we know today as Usul was not shaped from the beginning, but over time this concept merged with several other beliefs concept such as: monotheism, justice, prophecy, resurrection, and Imamate. These were grouped together as a set from the thirteenth century onwards.