Let me first attempt to state the questioner's viewpoint. Unless mAyA is already present, neither concealment nor projection can take place. Is mAyA then coeval with brahman? Do they exist side by side? Does this not contradict the non-dual status of brahman? Where does mAyA operate? What is its base of operation? These questions raise very profound issues.
The base of activity of mAyA cannot be brahman because the latter is Absolute luminosity and there is no place in it for ignorance or darkness. Nor can the jIva be the base of operations of mAyA. For jIva itself cannot come into existence until mAyA has operated. There seems to be an irresolvable logical difficulty here.
But the difficulty will vanish once we realize that we are here making an implicit assumption that is not valid. We are actually assuming the prior reality of time and space before the appearance of mAyA. Otherwise we could not have asked the question: Where does mAyA operate? When does it come into existence? These questions are valid only if you have a frame of reference in time and space independent of mAyA. But time and space, says Shankara, are themselves creations of mAyA. (cf. `mAyA-kalpita-desha-kAla- kalanAt' in his dakshiNAmUrti-stotra, sloka no.4).
In fact, this is also the answer to the physicist's question: When did time originate? Time did not originate in a timeless frame because we would then be begging the question. The very fact that we are conscious of the passage of time is a consequence of mAyA. So questions such as, `Where does mAyA operate?' and `When did it start operating?' are not properly posed. Time and space cannot claim prior existence. It is therefore wrong to ask whether mAyA is prior to jIva or later than jIva. Ultimate Reality is beyond space and time. In the words of Swami Vivekananda, time, space and causation are like the glass through which the Absolute is seen. In the Absolute itself, there is neither space, nor time nor causation.
As in the field of modern physics, so in the field of vedanta, time and space are modes incidental to sense perception and should not be applied to what is trans-empirical. jIva and mAyA are both given a priori in our experience and we have to take them as such. They are anAdi (beginningless). The only relevant question that you can ask about them is about their nature and final destiny. Examination will show that mAyA is neither real nor unreal.
`I am ignorant' is a common expression, within anybody's experience. Hence mAyA is not completely unreal. But it disappears with the onset of knowledge. So it is not real either. Thus it is different from both the real and the unreal. In Sanskrit it is therefore called `sad-asad- vilakshaNa', meaning that it is different from both the real and the unreal. And for the same reason it is said to be `anirvachanIya', meaning, that which is undecidable or that which cannot be defined one way or the other. It is in this sense we say that the world of perception, the common world of experience, cannot be rejected out of hand as totally false, like the hare's horn or the lotus in the sky; nor can it be taken to be totally real because it suffers contradiction at a higher level of experience. It is real in the empirical sense and unreal in the absolute sense.
This is also the case with a dream. For the dreamer, the dream is real. The acceptance of the reality of the dream to the dreamer is the king-pin of Shankara's explanation of Advaita. He bases many of his arguments on this phenomenal reality of the dream. This reality, called `vyAvahArika-satyaM' is in between the total unreality - `asat' - of the barren mother, and the total reality - `sat' - of brahman. The dream and similarly the perceptible universe is neither `sat' nor `asat'. It is `mithyA'. The meaning of the word `mithyA' is not falsehood but comparative unreality. It is not total non-existence like hare's horn but it is midway between the absolute truth of brahman and the absolute falsehood of hare's horn.
There are actually different analogies to explain the peculiar relationship between brahman and the universe. The analogy that Shankara very often uses is the relationless relationship of the rope that is mistaken for the snake, because of poor lighting. The rope appears as a snake no doubt, but actually there is no snake there, ever. Even when it appeared to be there, it was not there. But the one who saw it did really get scared on `seeing' the snake and only when help came in the form of better lighting did the person realize that what `was there' all the time was only a rope.
The second analogy that is used in the literature is the appearance of water in a mirage. And the third one is that of the dreamer and his dream. Each of these three analogies has its own limitation in explaining the relationship between brahman, which is invisible, and the universe, which is visible. Brahman is the rope; the visible universe is the snake. What appears as the universe is not really the universe. When spiritual illumination takes place we will know that what was there all the time was only brahman. Similarly in the example of the mirage and water, the water appearance is only an illusion. What is there in reality is only sand, no water. The dream of course is totally a mental aberration, fully subjective and it vanishes the moment the person wakes up.
The three analogies are not however just three analogies in place of one. There is a gradation, says Ramana Maharshi. First it may be questioned, with reference to the analogy of the rope and the snake that when the lighting situation improves the appearance of the snake is no more there, whereas, in the case of brahman versus universe, even after learning that brahman is the substratum of truth, and the universe is only a superimposition like the snake on the rope, we still continue to see the universe; it has not disappeared!
For this the Maharishi wants you to go to the analogy of the mirage. Once you understand it is the mirage and no watershed, the appearance of water is no more there. But now there is another objection: 'Even after knowing that there is only brahman and the universe is only an appearance, one gets certain wants fulfilled from this appearance of a universe: one gets one's hunger satisfied, thirst quenched and so on. But the water in the mirage does not quench one's thirst; so to that extent the analogy is inappropriate'.
The analogy of the dream meets this objection, says the Maharishi. The dreamer has his thirst quenched in the dream. The thirst itself is a dream thirst and it is quenched by drinking (dream) water in the dream; so also the wants that one feels in this universe like hunger and thirst are also quenched by corresponding objects in this universe. Thus in this sense the analogy of the dream is reasonably perfect. Maybe that is why Shankara uses the analogy of the dream so emphatically to describe the reality or unreality of the universe.
In Advaita the concept of reality is always comparative. Relative to materials, things made out of the materials are unreal. In other words if a bucket is made out of plastic, the bucket is unreal relative to the plastic. It is the cause that is `more real' than the effect. The cause of the world versus the world itself gives us a comparison about their relative reality. When we say that the universe is unreal, we mean that it is unreal as the universe, but it is surely real as brahman, its cause.
In order to explain this relative unreality the theory of superimposition is meticulously worked out by Shankara. While the snake is superimposed on the rope, the rope undergoes no aberration or modification in the process. It is the same rope all the time. What appears to you is only in your mind. The visible universe is just a perishable (kShara) superimposition on brahman. Brahman does not undergo any change in the process. All the time brahman remains as brahman, the imperishable (akShara) substratum. This is where the nirguNa (attributeless) character of brahman is effectively applied by Shankara to his explanation of this mysterious relationship.
This phenomenon of brahman not being visible but something else, the universe, being visible, is exactly what the term `mAyA' means. It does two things. It hides brahman from you. Simultaneously it projects the universe to you.
The declaration that this is what is happening comes forth from the Lord Himself in Gita IX - 5, 6. 'Everything that is perceptible is pervaded and permeated by Me, who is unmanifested. All the beings are established in Me but not I in them; they are not in Me either, this is my divine yoga.'. He remains unmanifested while what is visible is basically a permeation by him. While he remains unchanged, and imperceptible, the universe is what is perceptible. Everything visible is supported by Him as the only substratum, whereas He Himself is not supported by anything. He is His own support.
The snake appears on the rope, the rope does not undergo any change, but the snake is supported by the rope, (meaning, without the rope there is no snake). But in reality the snake was never there and so it is also true to say that the snake is not in the rope. To the question: Where is the snake?, the answer is: it is in the rope. To the question, Is the snake there?, the answer is, there is no snake, the snake was never in the rope. It is in this strain that the Lord gives out, almost in the same breath, what appears to be two contradictory statements. Everything is in Me; and nothing is in Me. This is the cosmic mystery of the existence of the Universe. It is and is not - sad-asad-vilakshaNa, mAyA!
More Resources: Shankaracharya's Advaita Vedanta
When we say 'I am', 'I' stands for the consciousness aspect and 'am' stands for the existence aspect. When we say ‘I am this’, there is the confusion of identification of the subject ‘I am’ with the object 'this'. That is due to error ,which is due to the ignorance of not knowing that 'I am'. Right now 'I am a jiiva' is the notional understanding while ‘I am Brahman’ is the vision of my self according to the Upanishads. That true ‘I am’ has to realized or recognized.
The body is only a vehicle or instrument required to exhaust my vAsana-s. Essentially, vAsana-s decide the type of body required - man or woman, white, brown or black skin etc. I, the jiiva, gravitate towards the environment that is conducive to my vAsana-s. Hence they are called 'kAraNa shariira' or causal body.
Hence what birth I take next depends on the most powerful vasana-s that are ready to germinate next. There is my ‘total bank account’ of karma (saMchita karma), of which I brought into this life only those that can be exhausted (prArabdha karma) and, if in the process I make new ones (AgAmin karma), which cannot be exhausted in this life, these are deposited to my account. Until all vasanas get neutralized, I will continue taking births in one form or the other. By yoga or sAdhanA, I neutralize the vAsanas. When I realize who I am - I am ‘not this, not this’ etc. (since I am the subject that can never be an object 'this') - I recognize that I am that sat chit ananda and then there is no more ownership of any karma. All are transcended in that knowledge of who I am.
As long as I think I am a jiiva, these notions are regarded as facts and Brahman does not come into picture – ‘I am Brahman’ is only realised from the state of absolute knowledge. Until this is recognized as a fact and not merely as a thought, jiiva-hood is there and vAsana-s operate. So karma and its kShaya (dominion) are there as long as you are there to question, since the questioning is done by a jiva.
As long as I am dreaming that I am being chased by a tiger, that dream tiger is as real as the one who is being chased. I have to run away as fast as I can to save myself from that tiger. Only when I am awakened to the higher state of consciousness, are the tiger and the one whom the tiger is chasing, as well as the forest and the ground upon which I am running, all resolved into my own mind.
The dreamer thinks that the dream world is real until he is awakened to a higher state where there is only one mind that projects the world of plurality. The plurality is real as long as dream lasts. The problem in your questions is that you want to place one leg in the waking state and one leg in the dream state and then question the validity of each from the other reference point. Any question from the Brahman viewpoint whilst still sitting at the jiiva position is like a dreamer asking about the waking mind. The waking mind is one – Advaita. The plurality of the dream world is from the viewpoint of a dreamer who thinks he is different from the tiger and the trees in the forest.