Sage Sri Sankara:- "The world, filled with attachments and avrsions, and the rest, is like a dream: it appears to be real as long as one is ignorant, but becomes unreal when one is awake.

Sage Sri Sankara:-  "The world, filled with attachments and avrsions, and the rest, is like a dream: it appears to be real as long as one is ignorant, but becomes unreal when one is awake.

Sage Sri Sankara:-  "As fire is the direct cause of cooking, so knowledge, and not any other form of discipline, is the direct cause of Liberation; for Liberation cannot be attained without Knowledge." (Self-Knowledge).

Sage Sri Sankara:-  As the moon appears to be moving when the clouds move in the sky, so also to the non-discriminating. Atman appears to be active when in reality the senses are active.

One can only know the universe is a mere illusion, when he discriminates between the three states and the formless witness of the three states.  Thus, it is necessary to understand the fact that, the formless witness is apart from the mind, which is present in the form of the universe and the universe appear as  the  waking or the  dream.    The mind or universe was non-existent in deep sleep.  The witness of the coming and going of the three states is birthless and apart. This has to be grasped mentally and    just as one knows a sound by its contrast to silence.

The one investigates  into the nature of the mind realizes the mind is   in the form of the universe. the universe  will never come to an end. For however many things may be known, there will always be more waiting to be known. They must realize the fact that, the nature of the universe is only an illusion; whatever they discover within the illusion, they will only discover only an illusion. Realizing this, they will have to turn to the formless substance and witness of the illusion  is consciousness. Thus the whole illusion,which is present in the form of mind or the universe is created out of consciousness. Thus the whole universe is consciousness. Thus  the consciousness alone is the real and the  universe is mere mirage.

When one denies existence of the soul, which is in the form of consciousness, he denies only the physical existence (universe); consciousness is the secret support of his denial. The universe is erupted from consciousness, sustained by consciousness and finally it dissolves as consciousness.  The   Illustration is: the dream. The dream has erupted from consciousness, sustained by consciousness and finally it dissolves as consciousness. The same way the waking experience also erupted from consciousness and sustained by consciousness and finally dissolves as consciousness. 

The consciousness,which is the formless substance and witness of the three states alone is permanent and the three states are impermanent. Those who cannot understand and analyze  the three states will always have trouble in grasping the ultimate  truth or Brhman.

Universe ,which is present in the form of the  mind is mere an illusion, but one cannot say it is an illusion  unless he becomes aware of the existence of the formless witness. It is there always, hence it is Impossible to be aware of three states without it.

There can be no such thing as a three states without the formless substance and witness, which is consciousness. No one can see the limitations of the witness i.e. the soul, the innermost  self. If one sees his limitations, then he sees  his body as self or witness, not the soul, the innermost  self, which is in the form of consciousness.

The universe ,which is present in the form of the  mind is only an object or seen, hence one tries to transcend it. Even consciousness is only an idea within the illusion. The universe is a mere an illusion  to the soul, the innermost self, which is present in the form of  consciousness. The subject (consciousness) as well as the object (universe or mind) is one in essence. Thus, everything (whole universe) is consciousness.   No second thing exists other than consciousness. Hence it is non-dual.