It is question of the Imamate which distinghishes the Shi'a sect from all other sects; it is the basic and fundamental difference which separates this school from other schools of thought. Other differences are not fundamental; they are "furu'i" (that is they are concerned with the details of the code of writing and action). Such differences of secondary importance are present between the views of the Imams (religious heads) of the majority community of the Muslims. For instance, a large number of the Hanafi laws do not correspond with the laws of Shafi'is. According to the Imamiyah sect, the Imamate is the rank of the Perfect Man; like prophethood it is sustained by Almighty God for the guidance of the people. The Shi'as believe that Almighty God ordered His Prophet (s.a.w.) to appoint 'Ali ibn 'Abi Talib (a.s.) as his successor, so that after the end of Prophethood the mission of spreading Islam might be continued. The Holy Prophet (s.a.w.) knew that this appointment would be looked at with displeasure by others. Many of them would think that it was due merely to brotherly love or undue regard for his son-in-law.

It is quite obvious tha from the beggining of the Islamic era until the present age of the Muslims have in genral not truely followed the Holy Prophet's guidance. The All-powerful declared in very clear words: "Oh Prophet, deliver immediately what you have been commanded to from your Lord and if you do it not, then (it will be as if) you have not delivered His message (at all)". Accordingly after his last hajj the Holy Prophet (s.a.w.) gathered the people at "Ghadir al-Khum" and addressed them thus: "Am I not better than every believer present here?" Then all of them said with one voice: "Certainly, O Prophet of God. You are superior to all of us."

After this testimony of allegiance the Holy Prophet (s.a.w.) said; "Whoever has accepted me as his master, then 'Ali is his master ..." Moreover, on various other occasions, the Holy Prophet (s.a.w.) clearly explained the reality of the Imamate, sometimes by implication and sometimes quite openly. The Prophet thus performed his duty and God's command his duty and God's command was carried out. As soon as the Holy Prophet had breathed his last breath some Muslims presumptuously tried to hide the reality of the Imamate. They misconstrued the open declaration, and through their personal interpretation began to make changes in the religious commands. The result is well known as we have seen.

However 'Ali (a.s.) and his group, which comprised high-ranking sahaba (companions) kept aloof from this selfish struggle for power and refused to offer allegiance.

Amir al-Mu'minin (a.s.) remained silent for some time, out of consideration for Islamic unity, but when Mu'awiyah tried to bring the Islamic rule and authority under his subjugation and started destructive activities, Amir al-Mu'minin set himself against him; supporting a man like Mu'awiyah and tolerating his wrong policies would have been a deadly poison for Islam, and it was the foremost duty of Hadhrat 'Ali (a.s.) to protect the divine religion.

The Imamiyah believe that spiritually they are with 'Ali (a.s) and are his followers; anyone who takes 'Ali as a friend, we too are friends of that person, and of whoever takes 'Ali (a.s.) as an enemy, we also are his enemy. This faith is based on the Holy Prophet's words: "Oh God, be a friend of the one who loves 'Ali (a.s.) and be an enemy of the one who is an enemy of 'Ali (a.s.)."

The Imamiyah Shi'as believe that Almighty God never leaves the world without a Prophet or an Imam whether this "proof of God" is apparent or hidden. The Holy Prophet (s.a.w.), through an explicit ordinance, made 'Ali al-Murtadha (a.s.) his successor. 'Ali (a.s.) made al-Hasan (a.s.) his successor, and Imam al-Hasan (a.s.) made his brother Imam al-Husayn (a.s.) his successor. In this way this chain continued until the eleventh Imam. The Eleventh spiritual guide Imam al-Hasan al-'Askari (a.s.) was succeeded by his son the twelfth Imam, the Imam of the Age, the Awaited One (a.s.), vicegerent of God. This belief is not an innovation of the Shi'as, rather it is a divine practice, which started with Adam (a.s.) and continued until the last Prophet (s.a.w.).