A Word Concerning the Unseen
The world of the unseen is the counterpart of the manifest realm, consisting of whatever lies beyond the scope of the senses and cannot be externally perceived. We have, for example, no direct knowledge of the circumstances of resurrection or the nature of reward and punishment, nor do we know anything of the composition of the angels or the attributes and essence of God, not because all of these are minute or subtle entities, but because they transcend our limited horizons of thought and lie outside time and space.
The unseen may be divided into two parts, absolute and relative. There are certain entities that are unseen in an absolute sense, for they will always be unseen by everyone and at all times, being intrinsically beyond the external senses of man, God's essence being an example of this. As for the relative unseen, this comprises entities that are manifest to some but unseen by others.
Everything that can be perceived by one of the five senses and thereby falls within the scope of man's sense perception counts as part of the manifest realm. This applies to matter and all of its effects, even if it be a question of items such as atoms, microbes and viruses which are invisible to the naked eye because of their minuteness. Our senses cannot perceive them unassisted, but once they are magnified several million times by means of special instruments they come within range of our perception.
Similarly, scientific discoveries of certain facts relating to this world full of secrets and mysteries, such as laser beams, x-rays' and gravity, do not relate to the world of the unseen, even though they appear to be imperceptible, for they are attained through the observation of natural causes.
This serves to demonstrate the limitations of our senses; even within the natural world they do not suffice for the perception of everything.
It sometimes happens that the sensory power of certain animals is much greater than our own. They can see things that are hidden from us or perceive them by non-visual means, whereas we can infer their existence only from the effects they produce.
As for the world of the unseen and what it contains, it stands in contrast to all the phenomena that are perceptible to our senses in one way or other and to some degree or other. Unable to perceive it with our senses, we can conceive of it only by means of rational proofs or the reports of those persons who do have awareness of it and the hidden matters it contains. Such persons guide us with their pronouncements to truths of which we would otherwise be unaware. This is a part of our creed and our faith.
Our deficient and limited beings are, then, imprisoned within the four walls of matter and we are deprived of perceiving many mysteries. In fact even our ability to perceive the phenomena of the sensory world is limited and conditional. Thus it is that for us being is divided into the two categories of the manifest and the unseen.
However, the hidden, non-sensory phenomena that are concealed from our perception are utterly clear and manifest to the Lord of the Worlds, the Creator Whose dominion and power embrace every atom in the universe and Who comprehends the totality of time and space. No obstacle hinders His infinite knowledge and unbounded power.
Past events that have been effaced from our memories and not even recorded in history, are present to God's view and observable by Him.
Paradise, hellfire, and resurrection, all of which are, from our vantage point, due to occur at some distant and unknown point in the future and the nature of which is utterly inconceivable, are present realities for God, the Creator Whose essence escapes all limitation and Whose sacred presence informs every part of the universe; He is aware of everything with out exception.
Phenomena that occurred billions of years ago or will occur billions of years from now are fully known to God. For us, however, the ability to conceive of past and future events is strictly limited by the fact that we exist within the confines of time and space, for we are material beings, and according to the law of relativity matter needs time and space for the process of constant change in which it is engaged.
God's knowledge is unmediated, immediate in the fullest sense of the word, although somewhat comparable to our own awareness of our selves. While His essence is utterly other than the phenomena He creates, neither is it separate from them; all things, past and present, are immediately present before Him.
Thus the Commander of the Faithful, 'Ali, peace be upon him, said: "Every mystery is manifest to You and every hidden thing present before You." 
He is aware of the totality of the atoms that make up the earth and the oceans, of the movements of all creatures, great and small, throughout the universe, and of the manifest and hidden aspects of all things. His knowledge is not restricted to that which has already occurred nor to creatures and phenomena presently existing; it also embraces the future.
If we were present everywhere instead of occupying a particular point in time and space, we too would be aware of all the truths and details of existence; nothing, great or small, would escape our expansive vision.
God's knowledge bears no similarity to human knowledge and is utterly incomparable with it; we cannot understand His knowledge by drawing all analogy with our own. Man's knowledge is dependent on the thing known having an external existence; the thing known must first exist, appear in the manifest realm, for man's knowledge to attach itself to it. Such is not the case with God's knowledge; there is nothing that is unseen for Him, and everything is manifest for Him.
Whenever we attain knowledge of something by means of our outer senses, it does not count as knowledge of the unseen. Conversely, knowledge the attainment of which does not depend on the five senses is the knowledge of the unseen.
All the phenomena of the material world can be said to have descended from a more perfect, non-sensory world, where they exist in a more elevated form. Now if we perceive the external aspects of things by means of our senses, thereby obtaining some portion of the truth, such perceptions do not count as knowledge of the unseen. If, on the other hand, we observe the hidden essences of things by means of our inner eye, discern their existential evolution, and thereby find the inner aspects of things divulged to us, without any involvement by our senses, the resulting knowledge with count as knowledge of the unseen.
The Qur'an says the following concerning God's knowledge:
"He knows the hidden and the manifest, and He is the Compassionate and Merciful." (59:22)
"He it is Who knows the unseen and the manifest, the Great, the Sublime." (13:9)
"O Knower of the manifest and the hidden, judge among Your servants in that concerning which they dispute." (39:46) "I know the hidden aspects of the heavens and the earth and that which you make manifest and that which you conceal." (2:33)
"Return, then to God, Who knows the manifest and the hidden; He shall make apparent to you all you have done." (62:8)
"He it is that knows the hidden and manifest dimensions of His creation; He is wise and well acquainted with all things." (6:73)
The Commander of the Faithful, 'Ali, peace be upon him, says: "He knows all things, but not by means of instruments and faculties the absence of which would negate His knowledge. His knowledge is not something superadded to His existence, interposed between Him and the objects of His knowledge; it is identical with His essence." 
A crucial issue arises at this point: is knowledge of the unseen exclusively God's and confined to His essence? Is it only for the Creator, Whose absolute being embraces the whole of the universe, that the unseen and the manifest are as one? Or can a human being also possess the ability to communicate with the world of the unseen?
Certain thinkers insist that knowledge of the unseen and awareness of hidden truths is restricted to God's essence. They maintain that even the prophets had no access to these matters, and they cite in support of their view a number of verses in which God, the principle of absolute perfection, mentions knowledge of the unseen as one of His distinguishing attributes, or the prophets reject categorically the possession of such knowledge.
"God holds the keys to the treasuries of the unseen; none is aware of the unseen except Him." (6:59)
"Say: 'I have no control over that which benefits me and that which harms me; it all results from God's will. Were I to be aware of the unseen, I would constantly augment that which benefits me and I would never suffer pain or loss. I am naught but a bearer of warnings and glad tidings to a people that believe.'" (7:188)
"I do not say that I have the treasuries of God, nor do I lay claim to His knowledge of the unseen, or that I am an angel." (11:31)
"Say: 'There is none in the heavens and earth but God Who knows the unseen, and they know not when they shall be brought back to life. '" (27:9)
"Say: 'I am a prophet, newly appeared, not different from the prophets who preceded me; I do not know what will befall me and you. '" (46:9)
"Among the people of Madinah are those who make a habit of hypocrisy, and you do not know who they are." (9:101)
From these verses it is concluded, then, that not even the prophets had access to knowledge of the unseen.
It is of course true that no one has absolute and complete knowledge of the unseen apart from God, Whose infinite existence embraces the whole scheme of creation; such knowledge is indeed confined to Him. Even though the prophets are in other respects superior to the rest of mankind, they too are limited in their beings and are inherently unable to have comprehensive knowledge of the world of the unseen. However, this limitation does not mean that the gates of the unseen are always closed to them and that God through the exercise of His will may not make it accessible to them, for He is, after all, the Owner of both the unseen and the manifest. Access to that realm is a gift that God may bestow on whomsoever He wills from among His messengers and other appropriate individuals. The knowledge that then results is a ray of God's own knowledge, pertaining to His essence; it is not autonomously acquired knowledge, distinct from His.
The verses cited above show that the people of the Jahiliyyah used to imagine that a prophet must have total control over the world and all it contains, and have the power of attracting to himself whatever is beneficial and repelling whatever is harmful.
God therefore instructs the Prophet, peace and blessings be upon him and his family, to refute these notions by categorically proclaiming that he had no such powers; that whatever powers he did have came from God; that whatever knowledge he had was derived from revelation and divine instruction; and that were it to be otherwise he would be able to uncover vast subterranean wealth for himself and, equipped with suitable foreknowledge, to ward off any evil.
Quite apart from these instructions, we find the Prophet himself denying the possession of such far reaching knowledge and power and attempting to convince men of the fact. However, at the very same time, we also find the Prophet being made aware by revelation of the evil plans of those conspiring against him and saved thereby from certain danger. The verses in question cannot therefore be taken to exclude totally the possession of any form of knowledge of the unseen on the part of other than God, nor can one overlook the existence of other verses which deal explicitly with the conveyance of knowledge of the unseen to the prophets.
The verse, "Say: 'I am not a newly appeared (prophet) among the prophets (who preceded me)'" (46:9), is intended to establish the principle that knowledge in all of its various forms does not spring up automatically from the Prophet, without his being dependent on the infinite source that is God's knowledge, any more than the knowledge of the preceding prophets was intrinsic to their own persons; for they, too, denied knowing what the future might hold in store for them without divine instruction and revelation.
As for the verse concerning the Hypocrites, it is obvious that their habitual practise of hypocrisy could bar the way to their identification by conventional means, but it does not exclude the possibility of being uncovered by other means; what the verse negates is the possibility of gaining knowledge of the unseen by the normal channels of cognition.
History in fact teaches us that the Prophet, peace and blessings be upon him and his family, not only knew who the Hypocrites were, but revealed their identity at the appropriate times to his confidants among the Companions.
Thus it is written that the Prophet, peace and blessings be upon him and his family, identified the Hypocrites to Hudhayfah, one of his close Companions and confidants. One day, the second caliph asked him: "Is there any Hypocrite among those I have appointed to various offices?"' He answered that there was, but refused to name the person in question until the caliph insisted that he did, with the result that the Hypocrite was dismissed.
It was also the habit of 'Umar never to participate in the funeral prayers for anyone unless Hudhayfah was present. 
Apart from this, it is obvious that no duty can be imposed on anyone unless he has the knowledge requisite for performing that duty, and we know that God entrusted the Prophet with the duty of doing battle with the Unbelievers and the Hypocrites and shunning their views, in the verse: "O Messenger, do battle with the Unbelievers and the Hypocrites, and he harsh with them" (9:73) Or again: "Do not obey the Unbelievers and the Hypocrites; assign their punishment to Us and place your trust in God." (33:48)
Is it possible that God should order the Prophet, peace and blessings be upon him and his family, to fight the Hypocrites and be harsh with them, and not to obey their wishes, while making it impossible for him to recognize them throughout the entirety of his life? Clearly we must conclude that the verse concerning their unknowability must have been temporary in its force, not permanent. 
In the following verses, the Qur'an establishes the principle that by God's command the prophets may gain access to the knowledge of the unseen:
"God does not make you aware of the mysteries of the Unseen, but selects for this station whomsoever He wills from among His prophets; believe, then, in God and His prophets." (3:179)
"This is knowledge of the unseen which We reveal to you." (3:44)
"He knows the unseen dimensions of the world and informs none thereof unless it be one with whom He is well pleased, such as one of the prophets, whom He sends angels to protect from in front and behind." (72:26)
This verse stresses that God alone is in His essence the true possessor of all knowledge concerning the unseen, and He will impart this knowledge only to those with whom He is pleased. To this category belongs the prophets for whom He appoints angelic guardians.
Elsewhere in the Qur'an God says:
"This Qur'an is the word of God conveyed by His (angelic) messenger (Jibril), an angel most powerful who enjoys high rank in the sight of the Lord of the Throne. He is the commander of the angels and the trustee of revelation. The messenger sent unto you (Muhammad) whom you call possessed is not possessed, for he did indeed witness Jibril, the trustee of revelation, at the highest point on the eastern horizon, and he does not begrudge you that which he has learned of the unseen (and if he were to judge fit, he would convey to you what he has learned of the unseen)" (81:19-23)
Here the Prophet, peace and blessings be upon him and his family, is declared innocent of begrudging others his knowledge of the unseen, and he is therefore implicity declared to possess such knowledge.
"God does not inform you of the unseen, but He chooses whomsoever He wills from among His messengers." (3:179)
What is at issue in this verse is God's choosing certain of His messengers for the bestowal upon them of knowledge of the unseen.
When we correlate and compare the two groups of verses, the indications contained in the verses themselves show that there is no contradiction. The first group of verses declare the impossibility of independent knowledge of the unseen on the part of any but God, while the second group points to God's conveyance of such knowledge to certain select and qualified people.
Revelation is in itself an unknowable mode of communication between God's messengers and the world of the unseen; it may be described as a ray of divine knowledge that He causes to shine on the hearts of His chosen servants.
It should also be pointed out that the prophets' knowledge of the unseen is limited and proportional to their capacity and degree of spiritual growth. Those who assert that the prophets, not to mention the Imams, have knowledge of the unseen do not claim that their knowledge is intrinsic to them or autonomous.
The sense of the two groups of verses is thus entirely clear: the first group negates the possibility of any but God having independent and total knowledge of the unseen, and the second group establishes that God may by an exercise of His will bestow a portion of that knowledge on some of His servants.
Apart from all this, any claim to messengerhood and prophethood is necessarily accompanied by a claim to communication with the world of the unseen by way of revelation. It would be utterly meaningless for someone to claim prophethood for himself but to renounce all claim to knowledge of the unseen. If the Qur'an stresses that the prophets have no independent access to that knowledge, it is in order to refute erroneous notions held in the Jahiliyyah concerning the extraordinary powers and attributes of prophets; it was thought that they utterly transcended all the characteristics of ordinary men and had superhuman knowledge of the whole of creation, enabling them to do whatever they wanted.
There can be no doubt that this Jahili view of the prophets would have prepared the way for them to be worshipped as superhuman beings. In order to prepare those infected by this mentality to accept the truth, the Qur'an therefore declares that like other men, the prophets engage in such activities as eating, walking and resting, and that their most important distinguishing feature is their receipt of revelation for conveying it to others.
The aim of the Qur'an is, on the one hand, to vindicate to men the truth of the messengerhood of the prophets in the communities from which they have arisen and, on the other hand, to refute erroneous notions concerning them and prevent them becoming the objects of idolatrous worship. Thus the Qur'an says:
"They say: 'We will never believe in you unless you cause a spring of water to gush forth, or produce a garden full of dates and grapes, with streams flowing through it; or cause the heavens to fall on our heads; or present us with God and His angels in visible form; or have a house built of gold; or ascend to the heavens. Nor will we believe that you went up to the heavens unless you bring back a book for us to read.' Say: 'God is exalted beyond my being able to bring Him or His angels before you in visible form; I am but a man whom God has appointed as a messenger."' (17:90-94)
"Again they said: 'Why does this messenger eat food and walk in the markets ? Why does no angel come to him in visible and sensory form, as witness to his veracity? Why does no treasure descend upon him, and why does he have no garden to eat of its fruits?'" (25:7-8)
This was the mentality of the Jahiliyyah the Qur'an had to combat.
 al-Radi, Nahj al-Balaghah,
 al-Saduq, Kitab al-Tawhid,
 Ibn al-Athir, Usud al-Ghabah,
Vol. I, p.391.
 Ja'far Subhani, Agahi-yi Sevvom, p. 184.