In his book about the Imamate, Shahīd Mutahharī expands on the Imamate from various angles in a highly accessible manner. He speaks about the three ranks of Imamate that depend on the role given to the Imam, drawn from the Prophet’s roles in the umma. His first role was being a prophet connected to heaven, Allah, the realm of the unseen, and revelation. In this regard, he was an explainer of the things he received from heaven. His second role was an adjudicator between the Muslims based on apparent proofs in all but exceptional cases, judging according to objective standards. His last role was the ruler of the Muslims, the leader of Islamic society, the guardian of the affairs of the Muslims, and the head of the state. In this regard, the Prophet practiced his duties based on Allah’s permission.
The idea of religious authority comes from the fact that the noble Prophet did not have the chance to explain the entirety of Islam to the entirety of the umma. New issues came up due to the expansion of the Islamic world, the Muslims’ mixing with other nations , and the development of the civil rule of the state and society. These factors made the umma need a period of time when it would rely on a scholarly authority. This authority had to be one that received Islam in its complete form from the Prophet, given to the Imam after the Prophet.