Reason as means to Self-knowledge or Brahma Gnana or Atma Gnana.+

The truth is beyond the scriptures and egocentric intelligence. Thus, in order to grasp, assimilate and realize the Advaitic truth the seeker to employ soulcentric reasoning faculty. The reason as a means to Self-knowledge or Brahma Gnana or Atma Gnana.
 
That is why Sage Sankara says in the commentary in Vedanta-sutra that what is accepted without a proper inquiry will not lead a person to the final goal. On the contrary, such acceptance will result only in evil, in something which is detrimental to our spiritual progress.

Thus, the seeker of truth should not believe blindly in traditional Orthodox nonduality without verifying all the facts from every angle. One has to reflect through reasoning over and over again without getting tired of the process.

There is no need to study the scriptures. One has to self-search for the truth and realize it without the scriptures. And then when he reads the scriptures he becomes aware the scriptures are also saying the same thing but everything is misinterpreted. 

Mundaka Upanishad:~ This Atman cannot be attained through the study of the Vedas, nor through intelligence, nor through much learning. He who chooses Atman ~by him alone is Atman attained. It is the Atman that reveals to the seeker Its true nature. (3 page70upanhsds by Nikilanada)

It means the ultimate truth is beyond the scriptures and egocentric intelligence. Thus, in order to grasp, assimilate and realize the Advaitic truth the seeker to employ soulcentric reasoning faculty. 

That is why Sage Sankara says: ~ VC ~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 that 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 utters the name of the medicine, without taking it; (similarly) without direct realization one cannot be liberated by the mere utterance of the word Brahman.

There is nothing more rational, more intelligible, and more un-dogmatic insights of  Sage Sankara is to drop all the theistic nonduality or Advaita which is meant for those who are incapable and not receptive to realize the ultimate truth or Brahman. 

Bhagavad Gita: ~ Reason as a means to reality. (Chap.18 verse 37)

In chap. 10 of the  Bhagavad Gita, Krishna says: ~ I cannot save you, but I can give you Buddhi (reason). (chap. 10)

In chap. 10 of in Bhagavad Gita, Krishna says: ~ "I have given you the most secret teaching, now reflect over it all" Krishna plainly says reflect, think. (Verse 63 of Chap. 18)

Mundaka Upanishad says: ~ Both states are harmful and take you away from the path of inquiry into truth. (Page 234)

Ashtavakra Gita: ~ It is not the absence of Buddhi (Reason) that can grasp Advaita but the man who possesses the highest intellect. Brains are necessary. Such a man, by merely hearing the truth mentioned will know it. (Page~ 224). 

There is no need for any philosophy in pursuit of truth because they take the seeker nearer to the truth, but they create more doubts and confusion.

 
Sage Goudpada: ~ To establish the truth of Nonduality by sheer reasoning alone. He begins by defining "What is real?" "What is unreal?" etc, because that is the right way to discuss or teach. People must first know what they are talking about. (Manduka Karika)

The reasoning is interpretable in two ways. The egocentric interpretation is to apply it only to the waking experience. The soulcentric interpretation is to apply it to the three states. The latter leads to a final settlement of the problems because it takes all data into consideration. 

As we keep digging deeper and deeper, the truth will shine as pure awareness in the midst of the duality (waking).:~Santthosh Kumaar