In verse 11 of the Isha Upanishad, the result of integration and acceptance of the “Knowledge” and the “Ignorance” is declared: “…by the Ignorance crosses beyond death and by the Knowledge enjoys Immortality.” How can we interpret and understand what is implied here? The Ignorance focuses on the manifestation of the universe. The Knowledge focuses on the Unmanifest. The Upanishad in its totality makes it clear that the egoistic standpoint of consciousness is an illusion, which, once overcome, brings us to a correct view of both our individuality and our Oneness with all forms and beings, the entire manifestation and the transcendent impersonal Brahman. Our entire understanding of birth and death changes when we recognize that the Multiplicity is an expression of the Oneness.
Sri Aurobindo explains: “By death is meant the state of mortality which is a subjection to the process of constant birth and dying as a limited ego bound to the dualities of joy and sorrow, good and evil, truth and error, love and hatred, pleasure and suffering. … the soul attributes to itself a certain portion only of the play of Prakriti or Chit-Shakti and consequently a certain limited capacity of force of consciousness which has to bear all the impact of what the soul does not regard as itself but as a rush of alien forces… [The ego] … can master by the understanding only so much of its experiences as assimilate with its own viewpoint and in a way which must always be imperfect and subject to error because it is not the view of all or the viewpoint of the All. … Death therefore is the constant denial by the All of the ego’s false self-limitation in the individual frame of mind, life and body. … It is only by accepting the oneness of the All that the individual can escape from this constant and necessary denial and attain beyond. Then All-being, All-force, All-consciousness, All-truth, All-delight take possession of the individual soul. It changes mortality for immortality.”
“The first necessity is therefore for man continually to enlarge himself in being, knowledge, joy, power in the limits of the ego so that he may arrive at the conception of something which progressively manifests itself in him in these terms and becomes more and more powerful to deal with the oppositions of Prakriti and to change, individually, more and more the terms of ignorance, suffering and weakness into the terms of knowledge, joy and power and even death into a means of wider life.”
“Immortality does not mean survival of the self or the ego after dissolution of the body. The Self always survives the dissolution of the body, because it always pre-existed before the birth of the body. The self is unborn and undying. … By immortality is meant the consciousness which is beyond birth and death, beyond the chain of cause and effect, beyond all bondage and limitation, free, blissful, self-existent in conscious-being, the consciousness of the Lord, of the supreme Purusha, of Sachchidananda.”
“Immortality beyond the universe is not the object of manifestation in the universe, for that the Self always possessed. Man exists in order that through him the Self may enjoy Immortality in the birth as well as in the non-becoming.”
Sri Aurobindo, The Upanishads, Isha Upanishad and analysis, pp. 21-23, 28 & 51-73