The Isha Upanishad in its short compass provides an outstanding basis for reconciling the Absolute in both its Negation and its Affirmation. Both the positive and the negative poles of knowledge and experience are viewed and accepted. The Knowledge and the Ignorance, the Birth and the Non-Birth, these apparent opposites are both necessary to have the complete knowledge.
Sri Aurobindo points out “The Absolute is in itself indefinable by reason, ineffable to the speech; it has to be approached through experience. It can be approached through an absolute negation of existence, as if it were itself a supreme Non-Existence, a mysterious infinite Nihil. It can be approached through an absolute affirmation of all the fundamentals of our own existence, through an absolute of Light and Knowledge, through an absolute of Love or Beauty, through an absolute of Force, through an absolute of peace or silence.”
The formula “not this, not that” is meant, not to deny the reality of the manifestation, but to avoid the impulse to circumscribe or limit the Absolute by what our minds can grasp. It is wider, higher, larger, more powerful, all-knowing, in relation to anything we can imagine. This formula is in fact not intended to be understood in the absence of the affirmative statement “All This is the Brahman” and “One without a Second”. These positive affirmations assure us of the Reality of the manifested universe, and the Unity of all.
The Upanishad states: “All this is for habitation by the Lord, whatsoever is individual universe of movement in the universal motion.”
Those who limit themselves by one side or the other of this knowledge creating duality out of unity, and multiplicity out of Oneness, caught in the limits of human logic which opposes Reality with its limitations, find eventually no solution to the riddle of life. Sri Aurobindo points out that the way of negation and abandonment of life is not the only way to approach the Reality of our Existence.