When one limits the consciousness only to the physical entity, it becomes ego.

The soul or  consciousness is the innermost self.  When one limits the consciousness only  to the physical entity, it becomes ego.  And ego is the cause of experiencing the duality as reality. Ego is the cause of the ignorance of formless non dual nature of the soul or consciousness. 

 Prior to experience of waking(mind or universe)  , there is only consciousness. The ego and the world  are part of the waking or dream.  The consciousness can remain with or without the waking or dream but ego ceases to exist without the waking or dream(universe or mind)

The mind or universe  is fully dependent on consciousness, whereas the consciousness is independent.   Therefore there is need to understand 'what is mind' and 'what is substance of the mind'  and 'what is the source of the mind',  in order to assimilate the Self-Knowledge or Brahma Gnana or Atma Gnana.

There is a controversy as to the meaning of Maya  or illusion in Advaitic schools. One Advaitic School says it is a Shakti of Brahman whereby both illusion and creation are brought about. But question is, how do one know what he knows is the ultimate truth? One cannot blindly accept on the sayings of Rishis and saints.  Even granting that they honestly believed in their experiences, there is still the query with what basis they have arrived at that conclusion, and on what standpoint they say it is illusion, because on the physical point of view the world is reality.  Therefore, it is for the seeker to find out by deeper thinking and reasoning to unfold the mystery of the mind/duality on his own, without the pondering into scriptures. 

Only deeper self-search  will help one to ascertain the truth of dual and non-dual experiences, which appear and disappear as waking, dream and deep sleep. 

The physical body and the world are mere experiences because they are within the waking or dream experience.  If one says it is mystic experience, then one’s experience differs from others and such disagreement does not settle the matter.

The Self-knowledge destroys ignorance and makes one free from experiencing duality as reality. Soul  or Consciousness or Spirit is the only Reality. Soul-centric reasoning  is the only tool to acquire Self-knowledge or Brahma Gnana or Atma Gnana.