The mechanism and criteria for appointing the Imam was one of the most significant, fundamental, and problematic elements of the early Shiite groups generally. In this paper, I will analyze this mechanism and criteria, which were taken by the early extremist Shiites concerning the Imamate, from the beginning until the 2nd century AH., by using a historical and discourse analysis approach. In addition, I will research the development and transformation of the Imamological viewpoint among the Saba’ iyya, Kaisaniya, the followers of Khurramdinan, whose thoughts were very similar to the above groups. Then, in this paper I will find out how the principles of knowledge (i’ lm), light (nur), and the transmigration of spirits have been used by the aforementioned groups to explain the concept of the Imamate. I will show how the two principles of light and the transmigration of the spirits, which were based on a specific worldview, with the assistance of early Ghulats, who emerged from the inner crisis of Kaisaniya, were used to explain the concept of the Imamate.