Fools dwelling in darkness, but thinking themselves wise and erudite, go round and round, by various tortuous paths, like the blind led by the blind.

People consider themselves to be knowledgeable because they have read books and well informed about the subject. But all these accumulated knowledge is not wisdom. One can’t get non-dual wisdom from accumulating knowledge.

Whether the knowledge accumulated are scriptures  or something from more recently published books are mere pointers to truth but not wisdom.  First, whether we're aware of it or not, as one reads he is imposing his own cultural conditioning, biases, experiences, and prior knowledge onto what he is reading; this is how his brains work. He “makes sense" of new things by associating them with things he already knows.

Most of the time, this is useful.  But if the "new thing" is utterly different from anything one has been exposed to before, he is almost certain to distort it to make it fit into pre-existing conceptual boxes. So much of knowledge   is about changing perspective, but that's hard to do when one is twisting the knowledge around to fit the perspectives he is already has.

Till wisdom is attained people generally use only intellect which is confined to waking state only. Intellect evolves into Reason as man realizes that study of the waking world is not enough, and that study of all the phenomena of mind, consciousness is required. Such study must embrace dream and sleep; hence there is no perfection of reason without analyzing the three states of consciousness.
 

Reason literally means 'that which distinguishes the ultimate reality from the rest.' When such discrimination between truth and falsehood by the method of reasoning is confined to the physical plane, it is intellect, logic, but when extended to the spiritual plane it is reason.

Spiritualistic reason is not based on ego but the formless soul, which is the innermost self. Soul-centric Reason is that which enables one to distinguish the real from the unreal, true from false. The intellectuals do not clearly know the difference between intellect and reason.

Knowledge derived from wisdom or Gnana is content- less existence, whereas intellectuality is the ordinary dualistic knowledge. Intellectuals have no idea of the first definition of it as yet because they are not aware of the existence of the formless witness of the three states. And they refuse accept anything other than their accepted truth which are based on the false self (ego) within the false experience (waking).  "Intellectuality” is a nothing to do with Brahmic – Gnana or non-dualistic wisdom. Intellectuality is useful   in practical life within the practical world. And its judgment is based on logical conclusions based on the ego which is not the self.   

Many intellectuals have a tremendous intellect; most will agree with their theories based on the ego, which is false self within the false experience. It does mean possesses Self –knowledge or non-dualistic Gnana? And knowledge based on the false self within the false experience is limited to false experience (waking) therefore it is certainly not self-knowledge or Brahma Gnana or Atma Gnana. 

 Katha Upanishad :-  Fools dwelling in darkness, but thinking themselves wise and erudite, go round and round, by various tortuous paths, like the blind led by the blind. (Upanishads Nikhilananda-Ch II-5 P-14)

It indicates that the one who is ignorant (darkness) of the true self (formless witness or Atman) searches truth by accumulating knowledge of every path and practice and uncertain about the truth, and thinks every path leads towards reality. The ignorance of the true self leads one towards unreality or hallucination.

Upanishads:- This Atman cannot be attained by the study of the Vedas, or by intelligence, or by much hearing of sacred books. It is attained by him alone whom It chooses. To such a one Atman reveals Its own form.(Katha Upanishad Ch-II -23-P-20)

All that is intellectual wealth, useful in explain doubts and difficulties if others rise them if you yourself encounter them in course of thinking. But to attain realization, all that is not necessary. You want fresh water to drink, but you do not require all the water of the river Ganges to quench your quest.

Upanishads:- They alone in this world are endowed with the highest wisdom who are firm in their conviction of the sameness and birthlessness of Atman. The ordinary man does not understand their way. (Chapter IV — Alatasanti Prakarana 95-P-188 in Upanishads by Nikilanada)

This passage indicates the fact that everything is Atman(soul or consciousness) . The one who views and judges the worldview on the base of his birth entity(body) will not realize the fact that, the man including the world is created sustained and finally dissolves as Atman. Thus Atman alone is, and all else is mirage.

Thus, self-knowledge is the aim of every human being. Since everyone thinks, the physical body is the self their aim is misdirected and they focus their attention on materiality, which makes one feel the duality (waking) as reality.

By focusing more attention on Atman by talking, writing, discussing only of Atman, the conviction grows and becomes firmer and the duality will fade away as reality. Atman, which is one’s true identity will prevail as birth-less and deathless, eternal substance and witness of the mirage called duality (waking or dream).

Gnana is usually translated as "knowledge" but that is because there is no equivalent word in English. It is more accurately "content less consciousness" or “self-awareness”.

Most think Consciousness usually implies something, thoughts or things, but it is the formless non-dual nature of the Atman or the soul. 

The consciousness exists with or without the matter because without the consciousness the matter ceases to exist because the matter is created out of consciousness.  It exists as matter in waking or dream.   And when wisdom dawns it is consciously aware of its formless non-dual true nature in the midst of matter, as in deep sleep.