Mastery over quoting the authorities from the scriptures and mastering the scriptural knowledge is not wisdom. Those who are conditioned by religion and yogic outlook find it difficult to grasp it. Until and unless there is strong urge to know, realize the truth, and reject the untruth, it is impossible to acquire the non-dual wisdom.
That is why Sri, Sankara [ V C] indicated that:-
56. Neither by Yoga, nor by Sankhya, nor by work, nor by learning, but by the realisation of one's identity with Brahman is Liberation possible, and by no other means.
58. Loud speech consisting of a shower of words, the skill in expounding the Scriptures, and likewise erudition - these merely bring on a little personal enjoyment to the scholar, but are no good for Liberation.
59. The study of the Scriptures is useless so long as the highest Truth is unknown, and it is equally useless when the highest Truth has already been known.
60. The Scriptures consisting of many words are a dense forest which merely causes the mind to ramble. Hence men of wisdom should earnestly set about knowing the true nature of the Self.
61. For one who has been bitten by the serpent of Ignorance, the only remedy is the knowledge of Brahman. Of what avail are the Vedas and (other) Scriptures, Mantras (sacred formulae) and medicines to such a one?
62. A disease does not leave off if one simply utter the name of the medicine, without taking it; (similarly) without direct realisation one cannot be liberated by the mere utterance of the word Brahman.
Holding some teacher or teaching as yardstick and trying to prove that he is right and others are wrong and indulging in perverse argument will help to unfold the mystery of the mind. Seeker has to learn to view and judge on the standpoint of formless witness (soul or consciousness, the innermost self), then he will be never having any doubts and confusion. When one thinks deeply then only the inner revelation starts and start burning the dross (confusion/doubts).
Deep sleep is merely used as illustration of soul, which is in the form of consciousness. If the one is sharp, enough he can get the glimpse of the soul/self mentally is as lightning flashes even in the midst waking the experience. Then it is called Natural Awareness.
Pursuit of truth will not end if one confines his-self to Waking state alone. In waking experience, it always produces, endless ideas and notions, hence it is restless state. Only in deep, sleep where there is no experience of duality. When this non-dual experience is brought into waking state consciously, then it is called natural awareness, the ultimate state.
Seeker of truth has to first realize the fact that, the Waking experience is also unreal, the same way as the dream experience. One must know wherever there is duality, it is mere illusion. Then only he will be able to elevate to the deeper level of understanding.
By analyzing the three states one becomes aware of the fact that the self is neither the waking entity nor the dream entity, but it is the formless knower [witness] of the three states, which come and go in succession. Illustration of dream shows that the power of the consciousness. Consciousness possesses the power to create the experience of duality (waking or universe) as reality and sustains and then subside it without any trace.
The deep sleep shows what power the consciousness possesses to reabsorb, store and reproduce the experience of duality [Waking or dream]. Finally having shown all three states analysis clinches and carries to culmination. The notionalistic theories based on the facts and show the nature or substance of the Waking experience is consciousness. Hence consciousness is not apart from it but it is in illusion creates the duality in consciousness and viewed judged each object is apart from one another. Therefore, whatever, the Waking experience contains the cosmos people and creates and animals are made out of one and only substance that is consciousness. Since there is, no other material other than consciousness the witness is bound to be consciousness.
If the consciousness becomes aware of its non-dual true nature it automatically establishes itself in its true state and views experience of duality (waking or dream) as illusion. Therefore, it will be at once free from the bondage and burden of the Waking experience, which was, considers as real as snake it becomes a rope or falsehood.