There are, of course, powers of mind that exceed the reactive sense-mind and the basic pool of consciousness in the lower nature of body, life and mind. The Buddhi is the term used to designate the higher degrees of conscious thought and will potential in the human individual. Sri Aurobindo has identified three successive gradations of the powers of the Buddhi that play a role in the establishment of the higher ranges of mental development as a guiding and directing force for life in the world:
“There is first an inferior perceptive understanding which simply takes up, records, understands and responds to the communications of the sense-mind, memory, heart and sensational mentality. it creates by their means an elementary thinking mind which does not go beyond their data, but subjects itself to their mould and rings out their repetitions, runs round and round in the habitual circle of thought and will suggested by them and follows, with an obedient subservience of the reason to the suggestions of life, any fresh determinations which may be offered to its perception and conception.” This first level is the one that expresses itself first and operates most commonly in the mental development of human beings.
“Beyond this elementary understanding, which we all use to an enormous extent, there is a power of arranging or selecting reason and will-force of the intelligence which has for its action and aim an attempt to arrive at a plausible, sufficient, settled ordering of knowledge and will for the use of an intellectual conception of life.” This development of the Buddhi “…creatse a certain kind of intellectual structure, frame, rule into which it tries to cash the inner and outer life so as to use it with a certain mastery and government for the purposes of some kind of rational will. It is this reason which gives to our normal intellectual being our set aesthetic and ethical standards, our structures of opinion and our established norms of idea and purpose. It is highly developed and takes the primacy in all men of an at all developed understanding.”
This organizing and structuring power is however, not the highest action of the Buddhi: “But beyind it there is a reason, a highest action of the Buddhi which concerns itself disinterestedly with a pursuit of pure truth and right knowledge; it seeks to discover the real Truth behind life and things and our apparent selves and to subject its will to the law of Truth. Few, if any of us, can use this highest reason with any purity, but the attempt to do it is the topmost capacity of the inner instrument, the antahkarana.”
Sri Aurobindo, The Synthesis of Yoga, Part Four: The Yoga of Self-Perfection, Chapter 5, The Instruments of the Spirit, pp. 624-625