When one becomes aware of the fact that, the 'self' is not the waking entity(form or body) than the waking experience(universe or mind) is mere illusion.

 Many seekers preconceived idea that,  by focusing on the single thought will lead them to realization of self. But it is not so. There is no doubt thinking is the tool, but the thought is the obstacle in the pursuit of truth. Thus thought is not the key to overcome the experience of duality but thinking deeply  and grasping is only a tool in pursuit of truth.

One has to realize the waking experience (duality)  is prior to the thought. The thought is the individual experience within the waking experience (duality or mind) . The thought rises only when the waking experience [duality or mind] is present. Thoughts bifurcates each and
every object within the waking experience (duality). Therefore, unity of thoughts is an impossible venture. Because it creates the feeling that, the person is an individual separate from the world, whereas, the person and the world are within the waking experience (duality or mind). in reality  the man and his experience of the world are one in essence.

Mind is in the form of universe. Universe appear as waking or dream. Waking   appears disappears and reappears.  waking experience is   the present  practical life within the practical world.  Waking experience is the stage where  the present birth life and death takes place. Waking experience is the state of ignorance. Ignorance is cause of experiencing the illusion as reality.  To overcome the ignorance the waking entity has to become aware of the existence of the formless witness of the three states. The formless, soul is the witness of the three states ,which comes and goes in succession.  the soul, is in the form of consciousness. the soul or  consciousness  is the innermost self. on the standpoint of the innermost self the three states are mere illusion.

 It is necessary to mentally  trace the  formless witness of the three states   in order realize the  fact that, the 'self' is neither the waking entity nor the 'self' is the dream entity but the 'self' is formless soul ,which witness the the coming and going of the three states. When one becomes aware of the fact that, the 'self' is not the  waking entity(form or body)   than the  waking experience(universe or mind)  is mere illusion.

Man and his individual experience of the birth life and death are reality within the falsehood. Until one has a firm conviction he is an individual separate from the universe and universe existed prior to him, and he is born in it afterwards he will never be able to acquire non-dual wisdom. Because of this reason he will not be able think beyond form, time and space.    Until this conviction is there all his views, judgments and conclusions are based on the false self within the false experience. Thus there is a need for overcoming this conviction by realizing the fact that the self is not form but self is formless. 

Without overcoming this conviction one is in the grip of form, time and space.  Until self is in the grip of form, time and space, the duality will prevail as reality.  If duality prevails as reality the ignorance prevails.  If ignorance prevails the wisdom will not dawn.  Without wisdom detachment to attachment is impossibility. 

Consciousness alone which is permanent and eternal, unchanging in the changing world is reality. People hear of Brahman or ultimate truth. People can only imagine it. One requires words only to distinguish between is there and not there, but he can’t posit either of Reality, because his saying so is only an idea, not reality. Ultimate truth is beyond words. Words are of use, however, as a thorn to pull out the thorn of other words that hinder knowledge.

Intellectually knowing the truth is only an imagination, whereas realizing the truth is knowing it as such.