Not only according to the Islamic and Qur'anic belief, but according to all religions, the first man was not only more developed that all the subsequent men; but was more developed than even the modern man. From the moment he stepped his foot in the world the first man was the vicegerent of Allah as well as His Prophet. It is a point worth consideration why the first man who appeared, appeared as a Divinely appointed authority and Prophet, while it seems more natural according to the evolutionary process that first ordinary men should appear and after they have attained a fairly high degree of development, one of them be appointed a Prophet.
According to the Qur'an the first man held a very high position: When your Lord said to the angels: "Surely I am about to place a vicegerent in the earth, they said: Will you place therein one who will do harm in it, and will shed blood, while we hymn Your praise and sanctify You? He said: Surely I know that which you know not. And He taught Adam all the names, and then showed them to the angels, saying: Inform Me of the names of these if you are truthful." (Surah al-Baqarah, 2:30-31 )
In short the first man who came into being caused surprise to the angels. What is the secret of this? In respect of the first man the expression, I breathed in him of My spirit (Surah al-Hijr, 15:29) has been used. This shows that the structure of this being had in it a higher element besides the material elements and it is this higher element which has been described by the above expression. In other words in the structure of this being something very special was put by Allah, who made him His vicegerent: "I am about to place a vicegerent (My vicegerent) in the earth." (Surah al-Baqarah, 2:30)
Thus the Qur'an gives the impression that the first man who stepped his foot on the earth did so as a Divine authority, a Prophet and a being having contact with the unseen world. Our Imams have laid stress on this origin of man in order to establish that the last man on the face of the earth would also be holding the same dignified position as the first man. Actually the world of humanity can never be devoid of a being possessing the spirit of I am about to place a vicegerent in the earth. The existence of all other men depends on his existence. If such a man does not exist, others also cannot exist. Such a man is called 'Divine authority'. By Allah, the world cannot be devoid of an authoritative master appointed by Allah . This sentence has been extracted from the sayings of Nahjul Balaghah and quoted in many books. I have heard the late Ayatullah Burujardi citing it, said that it was a sentence which Imam Ali pronounced while in Basra and that it was regularly reproduced both by the Shi'ah and the Sunnis. This sentence is the concluding part of a tradition reported by Kumayl. He says that one day Imam Ali caught hold of his hand and took him out of the city. When they reached a secluded place known as Jabbin, Imam Ali heaved a deep sigh and said: "Kumayl, the hearts are receptacles. The most retentive of them are the best. Therefore remember what I tell you. The men are of three types: a Divine scholar, a pupil seeking salvation and a buzzing fly". (See Nahjul Balagha, Saying 146). According to Imam Ali's terminology a divine scholar is not an ordinary scholar, although we often apply this term indiscriminately. He means a scholar 100 per cent devoted to Allah. In this sense perhaps this term can apply only to the Prophets and the Imams. The second group is that of the pupils who receive knowledge from the first group. The third group is of those "who have not sought the light of knowledge and have not resorted to a strong support." After saying this Imam Ali complained of the people of his time. He said that he had great amount of knowledge to impart, but he did not find any one fit to receive it. He added that there were some people intelligent enough, but they wanted to use what they learnt to gain their selfish ends and to exploit religion for their worldly gains. Therefore he had to withhold knowledge from them. There were others who were good people, but they were fools. They did not understand or understood wrongly. From what Imam Ali said so far it appeared that he was totally disappointed. But that was not the case. He was talking of the majority only, for he added: "No, not indeed: The earth is never without a divine authority, whether visible and known or hidden and unseen. The existence of such an authority is necessary so that Allah's proofs and arguments may not become invalid. But how many and where are such people? Indeed very few, but very dear to Allah. It is through them that Allah preserves His proofs and arguments. They pass on their knowledge to their likes and cultivate it in the hearts of their counterparts."
Speaking further about these individuals who receive their knowledge from Divine source, Imam Ali said: "Knowledge rushes to them giving them insight into the truth." In other words their knowledge is intuitive, not acquired, and is free from every error and mistake. "They are endowed direct with the spirit of conviction", for they are in direct touch with the unseen world. "What is difficult for those who are accustomed to luxurious living, is easy to them. "The most difficult thing for those who live in ease and luxury is to devote themselves to Allah." "They are familiar with that to which the ignorant are averse. They live in the world while their souls are attached to the highest place." Their bodies are with the people in this world, but their souls are somewhere else. The people find them among themselves, but do not know that their souls are attached to some elevated place."
That is the logic of Imamat. That is the reason why there is a chapter in al-Kafi entitled, Babul Hujjah. Reports in this chapter say that even if only two persons were left in the world, one of them would be a hujjah or Divinely appointed authority. I propose to quote some extracts from the Babul Hujjah of al-Kafi so that you may become better acquainted with this logic. All other questions such as that the people must have an Imam so that he may dispense justice to them or so that he may resolve the controversies about religious matters, are subsidiary questions. An Imam is not required to administer the government and hence he is not to be chosen by the people. He is above all such things. The administration of government may be called a side business of him. Now we put forward selected words of various traditions so that the logic of Imamat may become clear.
A report from Imam Sadiq: This is a report relating to the Prophets. It is said that a zindiq (a free thinker or an atheist) asked Imam Sadiq how he could prove the existence of the Prophets and the Divine Messengers. The Imam basing his reply on the doctrine of monotheism, said: "We know for certain that we have a Creator, who is far above us and above all that He has created. That Creator is wise and sublime, but we cannot have direct contact with Him. It is not possible for His creation to see Him, to touch Him or to argue with Him. But we need His guidance, for He alone knows what is in our interest and what is beneficial to us. Therefore there must be some messengers of Him to convey His message to His creation and His slaves and to tell them what is to their advantage and what is detrimental to them. This proves that there are some admonishers appointed by Allah, the Wise, the All-knowing."
About these admonishers (Prophets and Imams) Imam Sadiq says: "They are wise men, wisely trained and sent with a wise message. They have been created exactly like other people, but still they are different from them." They have an additional dimension and an additional spirit. "They enjoy the support of the All-wise and All-knowing who has granted them wisdom. The existence of such a person is essential in every age and every period of time, so that the world may not be devoid of a master (hujjah) having signs showing his veracity and irreprochability."