Second-hand knowledge of the Self-gathered from books or Gurus can never emancipate a man until its truth is rightly investigated and applied.+

All the Gurus, teachings practices, bookish knowledge are on the dualistic perspective; therefore they will not help to cross the threshold of dualistic illusion.  The ultimate truth is based on the nondualistic perspective.

Tripura Rahasya: ~ Second-hand knowledge of the Self-gathered from books or Gurus can never emancipate a man until its truth is rightly investigated and applied; only direct realization will do that. Realize yourself, turning the mind inward. (18: 89) 

Nothing is needed to realize the truth beyond the form, time, and space other than realizing the form, time, and space are created out of single stuff.  That single stuff is the Soul, which is present in the form of the Spirit (consciousness.  Knowledge of the single stuff is Self-knowledge or Brahma Gnana or Atma Gnana.

Only a perfect understanding of ‘what is what’ is needed. By realizing form, time and space are one in essence and that essence is consciousness leads to non-dualistic or Advaitic Self-awareness. When we drop all accumulated knowledge and start afresh it becomes easier to acquire Self-knowledge or Brahma Gnana or Atma Gnana. 

Sages of truth restrained themselves parting the Self-knowledge or Brahma Gnana or Atma Gnana to the mass and only a selected few. It was hidden from the people who were not qualified and receptive to it. Self- it was given knowledge or Brahma Gnana or Atma Gnana was not written down but was imparted orally to the chosen few. Thus, religion was given to the mass, and knowledge of the spirit is given only to a selected few. Thus, we find traces of the knowledge of the Spirit in religious books in the form of parables. 

People consider themselves to be knowledgeable because they have read books and are well informed about the subject. But all this accumulated knowledge is not wisdom. One can’t get Advaitic wisdom from accumulating knowledge, which is based on the dualistic perspective. The dualistic-based knowledge is not Self-knowledge or Brahma Gnana or Atma Gnana.

Whether the knowledge accumulated is of the scriptures or something from most recently published books, are mere pointers to the truth but not wisdom. First, whether one is aware of it or not, as he reads he is imposing his own cultural conditioning, biases, experiences, and prior knowledge onto what he is reading; this is how his thinking faculty works. 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 he is twisting the knowledge around to fit the perspectives he is already having.

As one goes on digging mentally and on more things will be revealed to him through inner revelation, which makes him get A firm conviction of what is what.

The scholastic,  like all believers,  have to start with an assumption that there is some unseen Being or Power or World, and then they start to interpret this assumption, the pursuit of truth starts with the world, going up from the objective world to the truth by inquiry and Soul-centric reasoning.

No assumption, no faith, is needed in pursuit of truth, the ultimate truth demands deeper thinking. People do not want to think: it is too troublesome. Why worry about the ultimate truth, they say. This is their excuse, an alibi for being too lazy or incompetent to think. They do not want to be bothered to inquire and reason.

The reasoning is interpretable in two ways. The egocentric interpretation is to apply it only to the waking experience(mind). The Soul-centric interpretation is to apply it to the three states. The latter leads to the final settlement of the problems because it takes all data into consideration. 

When the ultimate truth is rightly known and one attains eternal life thereby. Through Soul, the innermost Self he gains strength and through its knowledge immortality.

 Not by intellectual speculation, but only by an awakening to the reality of his true existence, he gets the Soul-centric vision.  The Soul, the innermost Self’s nature is like the state of a deep sleep,  which is free from duality.

Religion, yoga,  and intellectualism are not the means to acquire Self-knowledge or Brahma Gnana or Atma Gnana.  Without getting rid of the ignorance and trying to get Self-awareness through religion and yoga is like a sleeping man trying to know what he is about, without waking up. As sleep is to the waking, so is ordinary life to the state of realization.

The seeker has to mentally grasp the existence of the formless witness (Soul or consciousness) of the three states, to realize the three states are merely an illusion. And mentally focusing attention on the formless witness constantly one will be able to establish the reasoning base on the base of the formless witness (Soul). And when the reasoning base is established on the base of the formless witness it becomes easy to understand and assimilate the Self-knowledge or Brahma Gnana or Atma Gnana. But it takes much time to establish in the consciousness because one has to overcome the physical conditioning by realizing the Self is not physical but is formless.:~Santthosh Kumaar