The word Imam basically means leader.
The word Imam basically means leader. Ali's two sons in succession, Hasan and Husayn, became Imams after him. After that, each Imam conferred the authority on one of his sons until the full number of twelve Imams was completed with Muhammad Al-Mahdi, who is believed to be still alive in occultation or hiding.
The concept of Imamate is based on the idea that there must be a living person who is a divine proof or demonstration of the existence of God and a vehicle of divine guidance or practical means for carrying out God's sovereign will. It fits into the Shiite configuration of basic faith principles. First is the unity of God, followed by belief in divine justice. Prophethood expresses the belief in verbal or written revelation.
The next logical step is practical demonstration of that revelation, and this is the Imamate. Finally, the Day of judgement expresses the principle of human responsibility before God. By now it is clear what we shall look for in the Bible. We shall look for evidence of God-given leadership authority. That authority will focus on human figures whose lives are evidence of the existence of God and who have the authority to interpret and apply the verbal revelation.
Factors associated with such leadership will be the symbolic value of the number twelve and the strange experience of occultation or hiding. In summary, our examination of the Bible focuses on the following clues of the Imamate: 1. human witnesses to the unity of God; 2. figures making verdicts on legal application; 3. figures in series of twelve; and 4. occultation. Genesis 1:26 and one or two other verses in Genesis speak of a man as the image of God.
Genesis one gives dominion to the man in God's image. This is just about as close to a definition of the Islamic Imamate as we can find anywhere. This aspect of image and dominion comes clearly through to the modern mind even in the West, even among Christians. It is interesting to note that the only dominion actually defined in Genesis one has to do with the sharing of food. One area is given to humankind and one area to other creatures.
Yet there is hardly a commentator in existence who recognizes the literal, textual limits of dominion. Nearly everyone jumps to the conclusion of Imamate, that the man has a true leadership role far beyond the boundaries of food. The principle of God-given leadership is so logical to the human mind that in such circumstances it is able to jump over so many steps of logic to reach it.