Each of the 3 Gunas, while acting throughout all levels of activity, has its own primary seat and strength in different parts of the being. Thus, Tamas is most active in the physical being, Rajas in the vital and emotional being, and Sattwa comes into its own natural sphere most effectively in the higher Reason and Intelligent Will, the Buddhi. When the Reason is heavily influenced by Tamas or Rajas, it is either cloudy, deluded or misled through the impulsion of desire. When there is a clear action of Sattwa, the higher Reason takes on its own true character and can guide and uplift the working and the consequent results.
Sri Aurobindo describes the sattwic intellience and will: “The sattwic understanding sees in its right place, right form, right measure the movement of the world, the law of action and the law of abstention from action, the thing that is to be done and the thing that is not to be done, what is safe for the soul and what is dangerous, what is to be feared and shunned and what is to be embraced by the will, what binds the spirit of man and what sets it free. These are the things that it follows to the degree of its light and the stage of evolution it has reached in its upward ascent to the highest self and Spirit.”
The sattwic intelligence not only uplifts the action of the human individual but also prepares and supports the eventual transcendence of the Gunas through the movement that leads to achievement of the divine standpoint. “There the soul is enshrined in light and enthroned in firm union with the Self and Spirit and Godhead. Arrived upon that summit we can leave the Highest to guide Nature in our members in the free spontaneity of a divine actino: for there there is no wrong or confused working, no element of error or impotence to obscure or distort the luminous perfection and power of the Spirit. All these lower conditions, laws, Dharmas cease to have any hold on us; the Infinite acts in the liberated man and there is no law but the immortal truth and right of the free spirit, no Karma, no kind of bondage.”
Sri Aurobindo, Essays on the Gita, Second Series, Part II, Chapter 19, The Gunas, Mind and Works, pp. 486-487