One may observe in moments of pure mental focus something of the nature of the true action of the thought-mind. Sri Aurobindo describes it: “So too the proper function of the thought-mind is to observe, understand, judge with a dispassionate delight in knowledge and open itself to messages and illuminations playing upon all that it observes and upon all that is yet hidden from it but must progressively be revealed, messages and illuminations that secretly flash down to us from the divine Oracle concealed in light above our mentality whether they seem to descend through the intuitive mind or arise from the seeing heart.”
We see here two basic operations; first, the application of the mind toward the outer world with a pure, clear observing faculty combined with a logical and reasoning ability that helps to sort, organize and manage information to achieve right understanding of what it is asked to observe; second, the function of the mind as a receiving station and conduit for the light and inspirations that come from levels above the mind, so as to bring them into the world of manifestation.
Unfortunately, the interweaving of the actions of the vital energy, manifested as the desire-mind, into the pure mentality, creates distortion and lack of receptivity that hinder these two operations. “…this it cannot do rightly because it is pinned to the limitations of the life-energy in the senses, to the discords of sensation and emotion, and to its own limitations of intellectual preference, inertia, straining, self-will which are the forms taken in it by the interference of this desire-mind, this psychic Prana. As is said in the Upanishads, our whole mind-consciousness is shot through with the threads and currents of this Prana, this life-energy that strives and limits, grasps and misses, desires and suffers, and only by its purification can we know and possess our real and eternal self.”
Sri Aurobindo, The Synthesis of Yoga, Part Two: The Yoga of Integral Knowledge, Chapter 8, The Release from the Heart and the Mind, pp. 336-337