Shia’s belief concerning the subject of caliphate and successorship to the Holy Prophet (s) is explained briefly as under:

1. The Imam or caliph after the Prophet (s) has certain duties and obligations the most important of which are the following: To explain the Quranic concepts and Shari'ah laws, to prevent the society from deviation, to answer religious and ideological questions, to carry out and establish justice and equity in the society, to safeguard the borders of Islam against the enemies.

2. The Imam and successor of the Prophet (s) must be scientifically and morally under a special divine attention and should be divinely trained and educated; that is, he like the Prophet (s) must be infallible and immune to all kinds of errors and mistakes. For this reason, the Prophet's successor is discerned and appointed divinely and introduced through the Prophet (s) or a previous Imam.

3. The divine will extends to the fact that the Prophet (s) introduces the Imam and leader after him and that he, by appointing Ali bin Abi Talib (a.s.) as his successor on different occasions, carried out this crucial duty.  That was why, Imam Ali (a.s.) considered himself as the Imam and the true and immediate successor of the Holy Prophet (s). He used to remind the people and the caliphs before him, on many occasions, that he was the caliph and that caliphate is divinely appointed and it had also been declared by the Prophet (s) many times.

4. The successors of the Prophet, peace be upon him and his family, are twelve immaculate Imams or "twelve caliphs" as reported in Shiite and Sunni sources. The first of them is Ali bin Abi Talib and the last of them is Hazrat Hujjat bin Al-Hasan Al-Askari (Imam Mahdi) – may Allah hasten his reappearance.

 5. The names of the twelve holy Imams and successors of the Holy Prophet are the following:
1. Ali bin Abi Talib, 2. Hasan bin Ali, 3. Hussein bin Ali, 4. Ali bin Hussein, 5. Muhammad bin Ali, 6. Ja'far bin Muhammad, 7. Musa bin Ja'far, 8. Ali bin Musa, 9. Muhammad bin Ali, 10. Ali bin Muhammad, 11. Hasan bin Ali, 12. Imam Mahdi (peace and benediction of Allah be upon them).[1]

The conclusion is that, following the demise of the Holy Prophet (s), a situation came into being as a result of which the Commander of Faithful, Ali (a.s.) who had been appointed by the Prophet (s) as his successor was deprived of his right to the caliphate. Thus, he was made to keep aloof in his house. But they sought his advice as and when they needed it. Indeed, for the good of Islam and Muslims especially the downtrodden, Ali (a.s.) despite being dissatisfied with the performance of the caliphate, never denied his advice to the caliphs.[2] For example, in some battles such as the battles with Persia and Rome, the Commander of the Faithful (a.s.) was consulted and he gave his suggestions despite being absent from the wars.

6. Shia believes that in order for a person's personality and character to be assessed and known, it is necessary that his conducts be properly examined and that his title or rank should not hamper or impede an investigation. Although being a companion of the Holy Prophet, peace be upon him and his family, is a matter of great pride, it does not imply that we should overlook his errors as we see that the Holy Quran has vividly reproached some of the Meccan migrants and the Medinite supporters for their mistakes[3] or those whose faith has been weak and their hearts sick.[4].