Within the framework of the normal mental processes, the action of the Buddhi, the reasoning intelligence and will, is always limited and imperfect. The perfection can only come about through a self-exceeding beyond this normal framework, and this occurs through a dual process which encompasses both a “negative side” and a “positive side”. On the “negative side”, it is a process of detachment and rejection of the impulses, demands, cravings and desires of the lower nature which color, limit and influence the action of the higher reason and will. On the “positive side”, there must be an expansion and heightening of the power of consciousness, through a process of systematic identification with the higher force that can work through the reasoning instrument and act from a standpoint of its native light and power.
Sri Aurobindo notes: “We find that it progresses towards a greater completeness in proportion as we arrive at two kinds of perfection; first, a greater and greater detachment from the control of the lower suggestions; secondly, an increasing discover of a self-existent Being, Light, Power and Ananda which surpasses and transforms the normal humanity.”
Each aspect of the mind is transformed through this process: “The ethical mind becomes perfect in proportion as it detaches itself from desire, sense suggestion, impulse, customary dictated action and discovers a self of Right, Love, Strength and Purity in which it can live accomplished and make it the foundation of all its actions. The aesthetic mind is perfected in proportion as it detaches itself from all its cruder pleasures and from outward conventional canons of the aesthetic reason and discovers a self-existent self and spirit of pure and infinite Beauty and Delight which gives its own light and joy to the material of the aesthesis. The mind of knowledge is perfected when ti gets away from impression and dogma and opinion and discovers a light of self-knowledge and intuition which illumines all the workings of the sense and reason, all self-experience and world-experience. The will is perfected when it gets away from and behind its impulses and its customary ruts of effectuation and discovers an inner power of the Spirit which is the source of an intuitive and luminous action and an original harmonious creation.”
In summary, “The movement of perfection is away from all domination by the lower nature and towards a pure and powerful reflection of the being, power, knowledge and delight of the Spirit and Self in the Buddhi.”
Sri Aurobindo, The Synthesis of Yoga, Part Four: The Yoga of Self-Perfection, Chapter 7, Purification–Intelligence and Will, pp. 641-642