Intellectuals may say the external world is a construction of the mind. But deeper inquiry and reasoning reveals the fact that, causal relation is never found between subject and object, and then there is no sense in intellectuals claim.
The waking or dream are not mere egoistic imaginations, but they are appearances. This must be understood. In dream the most important thing is that it ha appeared spontaneously, in dream the dream entity may be a minister or a doctor, or a peasant, and it is imagined or constructed by the waking entity. It is not the idea of the waking entity, which is present only in waking experience, but the soul, the innermost self , which is fully aware of the three states, which comes and goes in succession.
One may have seen the birth and death of other beings within the waking or dream, but one has never seen the birth and death of the knower or seer or witness of the three states.
One may imagine it but even that is possible within the waking or dream. In other words the formless witness of the three states must be there before their appearance. Hence the witness which is the true self, is termed "the unborn, because it is formless.
One has never seen the formless witness going, so one cannot call it mortal, because it is ever present in all the three states. It can remain with or without the experience of duality.
The three states (object) must be of the same stuff as the Seer (subject) of them because they disappear into soul or self or seer.
Upanishads says:_ What use are the scriptures to anyone Who knows not the one source from whom they come, In whom all gods and worlds abide? Only those who realize him as ever present Within the heart attain abiding joy. - Shvetashvatara Upanishad
Everyone is seeking eternal peace and misery is most unwelcome to all creatures. Every living creature is engaged in some activity or the other only in search of eternal peace. But they have not attained this peace because they are not aware of their formless true identity. Instead they have gotten themselves entangled only in pain and pleasure because they are not aware of the fact that, the self is not form but the self is formless. They have not been able to get this non-dual peace because they seek physical happiness from external objects, while the truth is that non-dual peace is within the mind and the search must be made within to attain this supreme peace, by investigating what is mind and what is the substance of the mind.
All the pleasures that are derived from the world are trifles compared to that non-dual peace which is the Supreme. Hence, it would the greatest help if one could show the way to this eternal peace. The Self-Knowledge is the tool to non-dual peace which is the nature of the true self, which is in the form of consciousness.
In the state of non-duality where there is complete cessation of sense “I am the doer ", "the objects that are seen or perceived are different from the self, which is consciousness", so on and so forth. In this state, there is no misery or delusion in the realm of non-dual truth. There is delusion or misery for the one who has realized this non-dual truth. “Because he is fully aware the experience is mere mirage created out of consciousness. Thus man and his universe is mere experience within the mirage. In realm of truth there is no mirage only non-dual reality.
The mixture of pain and pleasure is inevitable to all beings that are born within the illusion, which is in the form of universe. Until man thinks he is the doer he is action oriented. In the realm of action he thinks he is an individual separate from the world. As an individual he has the conviction that, he is born in this world and world existed prior to him. Until this conviction is there it is very difficult to grasp the non-dual truth.
Deeper inquiry, analysis and reasoning revels the fact that the self is not the form (body or ego) but formless (soul or consciousness). Therefore, if the self is formless, then, one which is born, lives and dies is not the self. If the self is birth-less then whatever seen, known, believed, experienced on the base of birth entity is mere myth. Thus the birth entity and its experience of the world is myth hence the world where the birth, life and death takes place is myth.
The universe which is in the form of mind comes and goes as waking or dream is unreal on the standpoint of the true self ,which is formless soul ,which is in the form of consciousness. The substance and witness of the mind or universe is consciousness. Since, the formless substance and witness are one in essence there is no scope for existence for second thing. Hence it is non-dual. Thus consciousness alone is real all else is mere mirage created out of consciousness.
As long as one believes the body as self, he is bound to believe his body as the doer. Until he thinks the body as the doer, he is bound to believe that, birth life, death and the world as reality. Until he believes the birth, life and death as reality he is bound to experience the illusion as reality. Without the consciousness the body and the world crease to exist.
The birth, life, death and universe are reality within the waking or dream. The waking or dream is unreality on the base of the true self, which is consciousness.
Hence if one wishes to overcome the experience of birth, life, death and universe (illusion), he has to realize the fact that, the self is not physical but the self is consciousness.
This awareness of the consciousness without physicality is possible for the individual only if the root cause for the ignorance is completely destroyed. Ignorance arises only if one sees the objects of the world as external to him. If there is no second object other then consciousness, then there is no room for any ignorance at all! Absence of ignorance leads helps one to overcome the illusory cycle of birth, life and death. Once a soul or self is out of this illusory cycle, there is no scope for experiencing the illusion as reality. Hence this self-awareness is known as "Liberation" or “freedom”.
To get freed from illusory reality, following the same track, one must get rid of the 'Notion of diversity' which is the root cause of experiencing illusion as reality. This is the road to non-dual peace, which is the nature of the true self.
How does one know that, there is no diversity at all, when we have the cognition of this entire universe with all varieties in its creation?
The truth which is consciousness is the only reality and that the apparent notion of diversity (the root cause of all miseries) is only due to ignorance. If this ignorance is destroyed once then the knowledge of consciousness arises. Then one becomes fully aware of the fact that the consciousness is ultimate truth.
Once this self- knowledge arises, one is able to disconnect identity with the ego and identify with the true self, which is the consciousness. Thus consciousness is ultimate reality.