The fact that some prophets are mentioned as "Imam" in the Holy Quran shows that the position of Imam is different from the position of prophethood and that it is a virtue for prophets. It also demonstrates that not all prophets had the power and capacity to reach this position.
Imam is an Arabic word meaning leader and commander and is one of the special terms in Islam. This word does not have a sacred meaning by itself and is used in the Quran for leaders who guide people toward God. But apart from this general meaning, it also has special meanings and uses in Shia Madhhab.
In a special sense, Imam refers to someone who has the position of Wilayat (leadership). Imam seeks to guide people on the right path. Imam is the best example of a perfect human being, and in fact, the happiness and perfection of a human being are manifested in Imam, because humans were created to realize the position of divine Wilayat; as we read in the Holy Quran: “We offered Our Trust (Our deputation) to the heavens, to the earth, and to the mountains, but they could not bear this burden and were afraid to accept it. Mankind was able to accept this offer but he was unjust to himself and ignorant of the significance of this Trust.” (Surah Al-Azab, verse 72)
The last two words of the verse mean that man can be at the top or at the bottom; therefore, man can have divine Wilayat or be “worse than lost cattle” (Surah Al-A’raf, verse 179); it means that man can be more misguided than animals and can also become God's prophet and His representatives.
“We appointed them as leaders to guide the people through Our command.” (Surah Al-Anbiya, verse 73) Therefore, Imams guide humankind and this guidance is done by God’s order. Imam is the mediator between God and mankind and is not limited to a particular religion.
The imam has three positions; the first one is divine dignity, which is the position of divine guardianship. This status is to the extent that God has taught him His special names: “He taught Adam all the names.” (Surah Baqarah, verse 31)
The second one is religious dignity. It means that individuals need to ask their questions about the religion from Imam.
The third position of Imam relates to society and is in fact a social one. This position goes back to the issue of guiding people. Because of closeness to God, Imam can guide people on the right path. Therefore, Imam has the ability to take the role of a caliph.
* This article was a summary of a speech made by Morteza Karbalaei, a professor at the University of Religions and Denominations.