The truth can be ascertained without the scriptures through deeper self-search.

The scriptural authority is not the proof or yardstick to judge the truth. Therefore, never use the scriptural authority to judge the non-dual truth.  The truth can be ascertained without the scriptures through deeper self-search.

Self is the substratum of the three states.  When the self is in ignorance than the three states, are experienced as reality. If the soul, the innermost self remains in its own awareness, than it is free from experiencing the illusory three states as reality.

Formless soul, which is present in the form of consciousness, is the innermost self. Consciousness   is the efficient cause of illusion and it itself is uncaused.  Thus cause of all cause is uncaused. Therefore cause and effect has no meaning on the on the base of formless soul or consciousness, the innermost self.

Self-knowledge or Brahma Gnana or Atma Gnana deals with knowing. It is dealing with the means to understand the nature of the dual and non-dual experiences which appear and disappear as waking, dream and deep sleep. Therefore scriptures are not necessary to analyze, our own three states.

  

Ignorance bars the way to liberation from expiring the duality as reality. Ignorance results from identification of the Self with the body.  The body and the world together is mind.  Thus limiting the mind to the body or waking entity is cause of the ignorance.  

Ignorance remains till duality is experienced as reality. When wisdom dawns the duality becomes mere illusion.  Thus we become slaves to attachment to the duality/falsehood. This is the cause of experiencing the birth, life and death as reality.  The idea of birth, life and Death makes one believe in the theory of rebirth because of our ignorance of the True Self. Transcendental knowledge of our True Self is Liberation, end of cycle of birth and death, and freedom from experiencing pleasure and pain as reality.

Since it is the vast subject it cannot be explained in few words, because the indescribable cannot be described but it has to be grasped and assimilated.