The Isha Upanishad describes the dual aspects of Reality, the Ignorance and the Knowledge: “Into a blind darkness they enter who follow after the Ignorance, they as if into a greater darkness who devote themselves to the Knowledge alone. Other, verily it is said, is that which comes by the Knowledge, other that which comes by the Ignorance; this is the lore we have received from the wise who revealed That to our understanding. He who knows That as both in one, the Knowledge and the Ignorance, by the Ignorance crosses beyond death and by the Knowledge enjoys Immortality.” (Isha Upanishad, 9-11, translation by Sri Aurobindo in The Upanishads)
The cosmic Ignorance is the detailed understanding of the manifestation, the powers, the interactions and principles of the entire creation in all its infinite and minute aspects. The cosmic Knowledge is the understanding of the Unity of all these apparently separate forms and forces. Either one, on its own, is limited and only a partial understanding. True understanding comes with the integration of both of these aspects.
When an individual becomes involved with all the forms and forces of existence and treats them somehow as separate, he is subjected to the dangers of being misled and manipulated by appearances. It is on the basis of the Knowledge that one can see both the independent action of the forms and forces, and also their interconnections and interrelationships, so that a balance and harmony can be maintained.
Sri Aurobindo comments on the Isha Upanishad: “By Vidya (Knowledge) one may attain to the state of the silent Brahman or the Akshara Purusha regarding the universe without actively participating in it or to His self-absorbed state of Chit in Sat from which the universe proceeds and towards which it returns. … By Avidya (Ignorance) one may attain to a sort of fullness of power, joy, world-knowledge, largeness of being, which is that of the Titans or of the Gods, of Indra, of Prajapati. This is gained in the path of self-enlargement by an ample acceptance of the multiplicity in all its possibilities and a constant enrichment of the individual by all the materials that the universe can pour into him.” (Sri Aurobindo, The Upanishads, pg. 63)
Sri Aurobindo writes: “There are in the cosmic consciousness two sides — one the contact with and perception of the ordinary cosmic forces and the beings behind these forces, that is what I call the cosmic Ignorance — the other is the perception of the cosmic Truths, the realisation of the one universal, the one universal Force, all the Vedantic truths of the One in all and all in one, all the various aspects of the Divine in the cosmic and a host of other things can come which do help to realisation and knowledge — provided they are taken in the right way. However all that can be best dealt with when it actually comes. It does not always come as soon as there is the widening — many pass through the widening of the consciousness to what is beyond the cosmic and take the cosmic in detail afterwards — and it is perhaps the safest order.”
Sri Aurobindo, Integral Yoga: Sri Aurobindo’s Teaching and Method of Practice, Chapter 7, Experiences and Realisations, The Cosmic Consciousness, pp. 184-187