The Tattiriya Upanishad, in one of its more memorable chapters, takes us through a series of steps undertaken by the student to learn the nature of reality. In each step, the teacher advises the student to go back and carry out “tapasya”, or “concentration of conscious-force” as Sri Aurobindo has translated it. And each time the student returns, he has expanded his insight to the next level of awareness, until finally he realises that the “bliss of the Eternal” is the Brahman and that it constitutes all that is, without a second.
Concentration of Consciousness-Force necessarily focuses the attention and the energy into a narrower compass, and so long as it retains its awareness and standpoint of being part of the larger whole, it is a power of Knowledge. But at some point in the concentration, if it focuses so intensely that it loses its awareness of all else other than the point being focused upon, it can give rise to what we call the Ignorance.
Sri Aurobindo explains: “Since Brahman is in the essentiality of its universal being a unity and a multiplicity aware of each other and in each other and since in its reality it is something beyond the One and the Many, containing both, aware of both, Ignorance can only come about as a subordinate phenomenon by some concentration of consciousness absorbed in a part knowledge or a part actio nof the being and excluding the rest from its awareness. There may be either a concentration of the One in itself to the exclusion of the Many or of the Many in their own action to the exclusion of the all-awareness of the One, or of the individual being in himself to the exclusion both of the One and the rest of the Many who are then to him separated units not included in his direct awareness.”
In each case, or in all of them, we see that it is the exclusive concentration in one direction or another which leads to the Ignorance and all of the implications of that Ignorance.
Sri Aurobindo, The Life Divine, Book 2, Part I, Chapter 13, Exclusive concentration of Consciousness-Force and the Ignorance