In the Taittiriya Upanishad, a series of steps in the development of consciousness are outlined. Starting from the material consciousness, the next step is the vital consciousness. What follows then is the mental consciousness, and thereafter, the “knowledge” consciousness (Vijnana or Gnosis, which Sri Aurobindo terms “Supermind”) and then the Ananda or Bliss consciousness. Thus, in the evolutionary progression, the highly developed mental consciousness will be superseded by the Gnosis or Knowledge Consciousness of the Supermind. As we see with the mental development, this does not occur in all its fullness all at once; rather, there are stages of development, a time for integration and consolidation of the gains, and then further development.
Sri Aurobindo notes: “The supermind, as we have seen, lifts up the action of the mental consciousness towards and into the intuition, creates an intermediate intuitive mentality insufficient in itself but greater in power than the logical intelligence, and then lifts up and transforms that too into the true supramental action. The first well-organised actino of the supermind in the ascending order is the supramental reason, not a higher logical intellect, but a directly luminous organisation of intimately subjective and intimately objective knowledge, the higher buddhi, the logical or rather the logos, Vignana. The supramental reason does all the work of the reasoning intelligence and does much more, but with a greater power and in a different fashion. It is then itself taken up into a higher range of the power of knowledge and in that too nothing is lost, but all farther heightened, enlarged in scope, transformed in power of action.”
Sri Aurobindo, The Synthesis of Yoga, Part Four: The Yoga of Self-Perfection, Chapter 23, The Supramental Instruments — Thought-process , pg. 824
Sri Aurobindo Studies 