The soul, the innermost self has to be free from experiencing the duality as reality. To overcome the duality, the waking entity has to know it itself is not the self but the self is the soul, which witnesses coming and going of the three states. Thus self-knowledge or Brahma Gnana or Atma Gnana is necessary to realize ‘what is truth’ and ‘what is untruth’ to reject the untruth by accepting the truth. :~ Santthosh Kumaar
Just as the sun is the direct cause of the daylight, so without the Self-knowledge or Brahma Gnana or Atma Gnana no emancipation can be had. Compared to all other forms discipline self-knowledge is the only direct means for freedom from experiencing the illusion as reality.
Only when the wisdom dawns the soul, the innermost self can remain in its own awareness in the midst of duality.