Through the natural process of the evolution of thought and conceptualisation, the dichotomy, albeit within an envelope of overall unity, developed in the Upanishads, eventually went to the logical extremes and created a more or less absolute dichotomy as a metaphysical position. Sri Aurobindo describes this as follows: “Since the knowledge of the One is Knowledge and the knowledge of the Many is Ignorance, there can be, in a rigidly analytic and dialectical view, nothing but pure opposition between the things denoted by the two terms; there is no essential unity between them, no reconciliation possible. Therefore Vidya alone is Knowledge, Avidya is pure Ignorance; and if pure Ignorance takes a positive form, it is because it is not merely a not-knowing of Truth, but a creation of illusions and delusions, of seemingly real unrealities, of temporarily valid falsehoods.”
This leads to the conclusion that the world created by and perceived through Avidya, Ignorance, is not ultimately real, and we come to the position of the world being an illusion or dream. True Knowledge in this view is that which denies and does away with these unreal creations of Ignorance and focuses exclusively on the Knowledge, the Oneness, the Unmoving Absolute.
This development has obviously moved far away from the synthetic and unified viewpoint we find in the Rig Veda and the Upanishads that at no time forgets that there is “one without a second” and that “all this is Brahman.”
reference: Sri Aurobindo, The Life Divine, Book 2, Part I, Chapter 7, The Knowledge and the Ignorance, pp. 491-492
Sri Aurobindo Studies 