From the viewpoint of Shi’ah scholars khilafat (caliphate) is a Divine office which is entrusted to the most distinguished, the most appropriate and the wisest person of the ummah (nation). The most clear line of demarcation between a Prophet and an Imam (Prophet’s successor) is that the Prophet lays the foundation of a religion, receives revelation and possesses a Book. However, as regards the Imam, though he does not possess any of these positions, yet, besides possessing the position of a ruler he is one, who explains and conveys that part of the Divine religion which could not be publicly narrated by the Prophet on account of lack of opportunity or because of the circumstances being unfavourable and, therefore, left it to his successors to tell them.