Sage Sankara meditation always means the critical analysis about the self to get salvation from the illusory duality (world).+

There is no hope for those who call themselves realists because they are unwilling to make an inquiry into what is real and what is falsehood. The true seeker indulges in deeper self-search, without relying on first impressions, and hence he is fit for the path of wisdom or truth.

The yogi is unfit for the path of wisdom. The yogi should realize that sitting quietly will bring him peace and not the truth, for he starts his quest without even knowing the meaning of truth. How then can he find the ultimate truth or Brahman?

The truth is not an agreement of different opinions.  The notion that truth is an agreement of opinion with fact, is unacceptable because impossible to attain. One cannot show that his opinion, i.e. his idea is the same as others.    Verification, the investigating and proving of truth, is absolutely necessary for the pursuit of truth to get un-contradictable truth.  The ultimate truth cannot be merely assumed it has to be proved.

Those who claim to have had occult experiences are like the insane because their experiences are similarly incommunicable to others. This breaks the first canon of science, i.e. truth must be communicable and verifiable. Facts must be communicable and verifiable to everyone, and not, hidden as "occult experience,” if they are to be true facts.

 The word Brahman means ultimate truth or reality which cannot be indicated by any word. The Brahman can be expressed through silence because it is beyond the experience of form, time, and space. Therefore, the word Brahma clearly stands for the essence of the three states, which is consciousness only. The final use of the pursuit of truth is to know that self is consciousness.

 Sage Sankara opposed the Buddhists only, who misunderstood Buddha and became atheists. According to Sage Sankara meditation always means the critical analysis of the self to get salvation from the experience of the illusory duality(world). Due to the eccentric ego of the then atheists, Sage Sankara did not go beyond this since the atheists will not accept God beyond themselves. This limitation is not due to limited knowledge of Sage Sankara but is due to the then-existing situation of the psychology of the surrounding society. Even Bhagavan Buddha kept silent about God because the society dealt with by Him consisted of Purvamimamsakas, who were strong atheists. Bhagavan Buddha says everything including the self is only relatively real (Sunya). This is correct because the self is a part of the universe, which is relatively real with respect to the absolute unimaginable God. Bhagavan Buddha stopped at this point because atheists cannot realize the existence of the unimaginable God indicated through His silence. 

The point of  Bhagavan Buddha is that if God is non-existent, the entire creation including the Self is non-existent. Sage Sankara wanted to establish the existence of the Brahman. For this purpose, He made the Atman as the Brahman. He brought out the identity of the Self with consciousness and made the Atman the Brahman. Since one will not negate the existence of his self, he will accept the existence of the Brahman, which is the Atman or Soul, the Self. Both Buddha and Sage Sankara kept silent about the absolute unimaginable God. The same philosophy was dealt with them at different angles in different situations.

The waking experience which is referred to as the witnessed and the Soul, the Self, which is present in the form of consciousness, referred to as the witness of the witnessed are wrongly looked upon by every one of us as equally real, though the waking experience has no reality in the absolute sense.

 The Soul, the Self, which is present in the form of consciousness, is the ultimate reality or Brahman or God in truth. 

The waking experience appears to be real in the same manner as,  when a  rope is mistaken for a snake, the illusory snake appears to be real.  The snake is said to be superimposed on the rope. The body and the world are within the waking experience. The waking experience is an object and the Soul, the Self, which is present in the form of consciousness is the subject.

All three states are an object to the Soul, the Self is the subject.  One finds the object and the subject are of different natures. Their relationship is of the form of superimposition of each on the other as also of their qualities, as a consequence of the absence of discrimination between the real nature of the witnessed and the witness of the witnessed. 

This is like the Association of a  rope,  nacre,  etc.,  with the superimposed snake,  silver, etc, owing to the absence of discrimination between them. The Association of the witnessed and the witness of the witnessed in the form of superimposition is described as false knowledge.    

After having known the distinction between, and the nature of, the witnessed and the witness of the witnessed one becomes aware of the fact that the witness and witnessed are one in essence. And that essence is consciousness.  Thus, from the ultimate standpoint, there is no second thing that exists other than consciousness, hence it is non-dual.

He who realizes the witness of the witnessed are one in essence and who has the firm conviction realizes the three states are unreal. Though the three states appear as real in the dawn of non-dualistic knowledge their unreal nature is exposed. :~Santthosh Kumaar