The ultimate truth or Brahman has to be proved without the scriptures.+

Sage  Sankara said:~Neither by the practice of yoga nor philosophy, nor by good works, nor by learning, does liberation come, but only through the realization that Atman and Brahman are one in no other way. (1) VivekaChudamani v 56, pg 25

The citations from scriptures are not proofs.  The ultimate truth has to be proved without the scriptures.  The ultimate truth is the universal truth and it does not belong to any religion.  Religion causes diversity in unity, whereas, the ultimate truth brings unity in diversity. 

That is why Sage Sankara himself says: ~ VC 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?

That is why Sage Sankara says:~ V C:~65- As a treasure hidden underground requires (for its extraction) competent instruction, excavation, the removal of stones and other such things lying above it and (finally) grasping, but never come out by being (merely) called out by name, so the transparent Truth of the Self, which is hidden by Maya and its effects, is to be attained through the instructions of a knower of Brahman, followed by reflection, meditation and so forth, but not through perverted arguments.

It is not that one should pore over the ancient scriptures.  There is no need to study first, and then realize. One has to realize first, then only he will know ‘what is the truth’ and ‘what is untruth’. One has to make his discoveries through the process of rational thinking.

He who has not rectified his reasoning  base from the ‘I’(form) base to Soul (formless) base  and one  who does not have the intense urge to know the non-dualistic or Advaitic  truth,  and who is not tranquil and subdued and whose mind is not receptive , cannot acquire Self-Knowledge  or brahma Gnana or Atma Gnana. 

When we realize that form, time, and space are one in essence,  then it leads to Advaitic  Self-awareness.  In Self-awareness,  even though there is diversity,  there is unity in diversity, because everything is created of the same stuff. That stuff is consciousness. There is no second thing that exists other than consciousness. :~Santthosh Kumaar