The Imam's Comprehensive
It is, then, the Imam, that being replete with virtue and overflowing with blessedness, who is aware of all the needs of the ummah and of whatever is conducive to a happy and dignified life, in this world and the hereafter, and plays a determining role in securing their spiritual and material well-being. He knows, too, whatever is needful for guiding men and administering their affairs and is fully aware of all matters, great and small, that arise as they traverse the ocean of life.
All these various types of knowledge and awareness derive from the comprehensiveness of the Imam and his functions, for his person represents a continuation or extension of the personality of Muhammad, the Seal of the Prophets, peace and blessings be upon him and his family. In his knowledge, characteristics and attributes, the Imam is like a representation of the Prophet in miniature, this being a particular favor granted him by God.
Once a leader comes to perceive the inner truth of the ordinances of religion and to possess a religious knowledge that is based on immediacy and certainty, not fallible mental exertion, it is inconceivable that he should be ignorant of any aspect of the Islamic sciences. How can one attribute ignorance of divine law to one who serves as a channel for divine grace and the guide of humanity?
It is the Inerrant Imam who as the guardian and treasurer of God's law creates the environment in which men may grow to perfection and advance on the straight path.
It is also one of his duties to preserve the doctrinal integrity of the ummah and its collective interests, for God's limitless mercy necessitates that humanity should never be left wandering and distraught, abandoned to its own devices. The leader must therefore be in a position to act as the spiritual and intellectual authority of the community by the gate of knowledge of God's commands being always opened to him so that by means of his instruction he can guide men to fulfil the purposes of religion. He constantly provides men with the means of solving their problems so that there is no excuse or pretext left for them to make. Answers to all kinds of conceptual and practical problems are contained in the thousands of traditions that have been transmitted from the Imams.
The firm and categorical responses they gave to all kinds of religious queries and doubts, their clear and rational refutation of various kinds of unbelief, their logical mode of dispute and argumentation all bear witness to the breadth of their Islamic knowledge and vision.
The one whose soul is more illumined than others, whose knowledge more elevated, whose vision more expansive, whose intelligence loftier, whose concentration more profound, and - most important of all who is equipped with the quality of inerrancy, such a one is better qualified to lead men than anyone else.
One whose knowledge is limited and the scope of whose religious perception is restricted is always in danger of acting in a sense contrary to the Qur'an, whether knowingly or not. There is no guarantee that his words and deeds will always accord with divine law, and if he were to contravene the Qur'an, so too would those who follow him. The source of the danger lies in the fact that his knowledge in many eases is suppositional, not definite, and there can be no doubt that someone who generally chooses the best among a series of possibilities may sometimes deviate from the path of the Qur'an without there being any evil intention on his part.
Imam al-Sadiq, peace be upon him, says in a certain tradition:
"God illumines His religion with the brilliant light of the People of the House and by means of them displays His sources of knowledge. The one who recognizes the Imam's claim to his obedience will taste the sweetness of faith and understand the superiority of Islam and its perfect and flawless nature, for God has made the Imam the banner of guidance and His proof to men, and placed on his head the crown of splendor and magnificence. The Imam is one whose whole being is submerged in divine light. He is aided with heavenly truths and the scope of his knowledge is unending God's bounties cannot be known except by means, and the Imam is thee means.
"Knowledge of God is not possible except by means of knowledge of the Imam. The Imam is versed in all the complexities of the revelation and the Sunnah, and is one whom God will always appoint from among the progeny of Husayn, peace be upon him." 
There are authoritative texts to the effect that whatever was taught to the previous prophets was also known to the Prophet, peace and blessings be upon him and his family, and to the Imams, peace be upon them. Thus Imam al-Baqir, peace be upon him, said: "God has two kinds of knowledge, particular and general. The prophets have no access to the former, nor can the cherubim become aware of it. It is the latter to which the prophets and the cherubim have access, and God's Messenger has transmitted it to us." 
Imam Musa b. Ja'far, peace be upon him, is reported to have said: "I swear by God that truths have been bestowed on us that were not given to Sulayman (Solomon) or anyone else. And recall God's address to Sulayman: 'This is Our gift to you; either teach it to others or keep it to yourself; you will not be called to account for it.'" (38:39) 
Imam al-Sadiq, peace be upon him, said:
"The one who has knowledge of the Book is 'Ali, peace he upon him, for he himself said, 'Be aware that the knowledge that came to earth with Adam, and all the knowledge with which the prophets were ennobled down to the Seal of the Prophets, exists in his progeny." 
He also said the following:
"The sacred divine essence has two forms of knowledge: one peculiar to God Himself, inaccessible to all men; and the other knowledge which is bestowed on angels and prophets. This second category of knowledge is accessible to us Imams too." 
Imam al-Baqir, peace be upon him, said:
"The knowledge that came down with Adam, the father of mankind, did not vanish, for it was handed down from one generation to the next. 'Ali had complete knowledge of religion and the shari'ah, and none of us (Imams) dies without designating a successor who will inherit his knowledge or whatever God wishes him to know." 
Again, he said: "We are treasurers not of gold and silver but of divine knowledge." 
The Commander of the Faithful, 'Ali, peace be upon him, says:
"God will never leave the earth devoid of His proof, the one who will rise up for truth, whether he be manifest among men or hidden from their view. The reason for this is that God's proof can never be disproved or disputed.
"How many are the proofs and where are they to be found? I swear by God that they are few in number, but their rank in God's presence is most exalted. God preserves His clear verses by means of them, for them in turn to entrust to those like unto them, and their accumulated treasure of knowledge is all marked by clear vision and certainty. What appears difficult to others is easy for them; they are at ease with intimidating problems from which the ignorant shrink back in fear, and they converse with those whose spirits are at the apex of loftiness and attached to the divine throne. They are God's viceregents on earth, guiding men to His religion." 
On many occasions during the lifetime of 'Ali, when problems arose that were beyond the capacity of the caliph to solve, 'Ali was the only authority to whom recourse might be had to find a solution. Conversely, not a single occasion can be found on which 'Ali turned to anyone else in order to learn something of Islamic law or find the solution to some problem or other.
Sa'id b. al-Musayyib is recorded to have said: "No one other than 'Ali b. Abi Talib ever said, Ask me my opinion, before you lose me.'" 
The one who assumes responsibility for the administration of the Islamic state must then be a person whose opinion will be a decisive criterion for the ummah in all that touches on the law of Islam. The Qur'an says: "Is the one who guides to God more fitting to be followed, or the one who himself needs guidance? How judge you this matter?" (10:35)
This verse constitutes an address to men's consciences, for the decision is left to them. Clearly man's conscience will dictate that he deserves to be followed who has discerned the true path, identified the truth, and summoned society to advance in its direction. One who himself needs someone else to aid him in the problems he encounters has no claim to being obeyed. Only a ruler who has no need of instruction by others in all the concerns of Islam may legitimately be followed and obeyed.
A Christian scholar by the name of Burayd once went to see Imam al-Sadiq, peace be upon him, in the company of Hisham b. Hakam. In the way they encountered Imam Musa b. Ja'far, peace be upon him, who asked Burayd how thoroughly he was acquainted with his own scripture. Burayd answered that there was none who could equal him in his knowledge of the Gospels. The Imam then asked him whether he relied on himself for the interpretation of the scriptures, and he replied that he had full confidence in his own understanding and knowledge.
Thereupon Imam Musa al-Kazim, peace be upon him, began reciting the Gospels. Burayd was astonished and profoundly affected. He said: "For fifty years I have been searching for one such as you." Then he embraced Islam, as did the woman who was accompanying him.
Hisham, Burayd and the woman then came into the presence of Imam al-Sadiq, peace be upon him, and Hisham related to him what had happened on the way. Imam Ja'far, al-Sadiq, peace be upon him, then recited this verse of the Qur'an as a description of Imam Musa al-Kazim: "Offspring, one of the other, generation after generation, and God hears and knows all that they say and all of their states." (3:34)
Burayd asked Imam Ja'far al-Sadiq, peace be upon him, how he knew the Torah, the Gospels, and the other books revealed to the prophets. He answered: "This is knowledge we have inherited. We recite and pronounce each of those books just as its followers and believers do. God would not place on earth a proof who would have to say in answer to any question, 'I do not know.'" 
al-Nawfali says: "After Imam al-Rida, peace be upon him, arrived, al-Ma'mun, the Abbasid caliph, gave that invitations to go out to various religious leaders to attend a meeting: the head of the Christian bishops, the leading Jewish rabbi, the leading starworshippers, people that followed no religious law whatsoever, the Zoroastrian judge, a Greek physician, and Muslim theologians all well versed in dogmatics. al-Ma'mun then sent a message to the Imam inviting him to participate in discussions with these religious leaders if he felt inclined. The Imam agreed to attend, and asked me what might be al-Ma'mun's purpose in convening such a gathering."
al-Nawfali answered that al-Ma'mun wished to test him and learn the extent of his knowledge. He next enquired of al-Nawfali if he feared that any of those luminaries might defeat him in debate, and he answered that far from entertaining any such fear, he was confident that God would permit him to triumph over them all. Then the Imam said: "Would you like to know when the caliph will repent of his initiative?" - "Yes."
"When I argue against the followers of the Torah by citing the Torah, against the followers of the Gospels by citing the Gospels, against the followers of the Psalms by citing the Psalms, against the Sabeans in their own Hebraic tongue, against the Zoroastrian priests in their own Persian tongue, against the Greeks in their own Greek tongue, and against the theologians in their own Arabic tongue; when I defeat all of them with my proofs and arguments so that they abandon their religions and accept the truth of what I say - then al-Ma'mun will understand that the seat of authority on which he resides is not rightfully his."
The next day, the meeting was convened at the appointed time, in the presence of the Imam. The leading Jewish rabbi said: "We will accept from you no argument that is not derived from the Torah, the Gospels, the Psalms of Dawud (David), or the pages revealed to Ibrahim." The Imam accepted this stipulation, and proceeded to prove with the utmost clarity that the Prophet of Islam, peace and blessings be upon him and his family, was the Seal of the Prophets. The arguments he advanced were so firm and unassailable that no doubt remained for anyone. The rabbi immediately conceded the truth of the Imam's words and embraced the truth.
Then the Imam engaged in similar debate with the scholars of other religions, and when they had all fallen silent, he said: "If any among you have further questions, do not hesitate to ask."
'Imran the Sabean, and unparalleled expert in theology, said: "I have been to Basrah, Kufah, Damascus and the Jazirah, and talked to all the theologians of those regions, but none among them was able to convince me of the oneness of God."
The Imam thereupon expounded in detail the proofs of God's unity, in the manner recorded in al-Saduq's Kitab al-Tawhid. The Imam's powerful arguments thoroughly convinced 'Imran, and he declared: "I bear witness that God is one as you have demonstrated and that Muhammad is His servant, sent by Him to guide mankind." Then he turned in the direction of the qiblah, prostrated himself, and embraced Islam.
At the end of the meeting, al-Ma'mun rose from the assembly, went inside with the Imam, and the people dispersed. 
The Commander of the Faithful, 'Ali, peace be upon him, said: "Make piety your rule and follow your Imam, for a righteous and just society will attain salvation by following a just Imam, and a corrupt and sinful society will be perished through following an impious and sinful leader." 
This tradition makes plain the direct connection between the moral characteristics of an Imam on the one hand and the ultimate fate of the society he leads On the other hand: the just Imam is the guarantor of a people's salvation and the evil leader condemns his following to perdition.
 al-Kulayni, al-Kafi,
Vol. I, p.203.
 al-Majlisi, Bihar al-anwar
Vol. XXVI, p. 160.
 Ibid., p. 159.
 Ibid., p. 160.
 al-Kulayni, al-Kafi,
Vol. I, p.255.
 Ibid., p.222.
 al-Bahrani, Ghayat
al-Maram, p. 514.
 al-Khwarazmi, al-Manaqib,
p. 390; al-Mu'jam al-Mufahras li Nahj al-Balaghah, p. 1407.
 al-Muttaqi, al-Hindi, Kanz
al-'Ummal, Vol. XV, p. 113.
 al-Kulayni, al-Kafi,
Vol. I, p.225.
 Hurr al-'Amili, Ithbat
al-Hudat, Vol. VI, pp. 45-9; al-Saduq, Kitab al-Tawhid, pp.
 al-Majlisi, Bihar al-anwar, Vol. VIII.