The purification of the higher understanding is a necessary precondition for exceeding the limitations of the mind as an instrument of knowledge; however, it is in itself insufficient to achieve the higher knowledge which is the object of the Yoga of knowledge. Sri Aurobindo notes: “But for real knowledge something more is necessary, since real knowledge is by our very definition of it supra-intellectual.”
At some point the mind must be prepared to become quiet and receptive to allow the higher powers of knowledge, that have their origin beyond the mental framework, to become fully active. In order to do this, Sri Aurobindo cites the need for “the power of intellectual passivity” which is of two kinds.
“In the first place we have seen that intellectual thought is in itself inadequate and is not the highest thinking; the highest is that which comes through the intuitive mind and from the supramental faculty. So long as we are dominated by the intellectual habit and by the lower workings, the intuitive mind can only send its messages to us subconsciously and subject to a distortion more or less entire before it reaches the conscious mind; or if it works consciously, then only with an inadequate rarity and a great imperfection in its functioning.”
Sri Aurobindo points out that a similar process is required to separate the intuitive mind from the higher reasoning intelligence to that which was undertaken to separate the sense-mind from the higher reason. “The remedy is to train first the intellect to recognise the true intuition, to distinguish it from the false and then to accustom it, when it arrives at an intellectual perception or conclusion, to attach no final value to it, but rather look upward, refer all to the divine principle and wait in as complete a silence as it can command for the light from above. In this way it is possible to transmute a great part of our intellectual thinking into the luminous truth-conscious vision,–the ideal would be a complete transition,–or at least to increase greatly the frequency, purity and conscious force of the ideal knowledge working behind the intellect.” This demands a passive stance of the intellectual faculty to recognise and be receptive to this higher form of knowing that originates beyond the framework of the intellect.
The second phase goes beyond even this receptivity: “But for the knowledge of the Self it is necessary to have the power of a complete intellectual passivity, the power of dismissing all thought, the power of the mind to think not at all which the Gita in one passage enjoins.” The power of the silence of the mind, so antithetical to the Western reliance on the thought process, is in fact, the necessary power to achieve this higher result. “But this power of silence is a capacity and not an incapacity, a power and not a weakness. It is a profound and pregnant stillness. Only when the mind is entirely still, like clear, motionless and level water, in a perfect purity and peace of the whole being and the soul transcends thought, can the Self which exceeds and originates all activities and becomings, the Silence fro which all words are born, the Absolute of which all relativities are partial reflections manifest itself in the pure essence of our being. In a complete silence only is the Silence heard; in a pure peace only is its Being revealed.”
Sri Aurobindo, The Synthesis of Yoga, Part Two: The Yoga of Integral Knowledge, Chapter 3, The Purified Understanding, pp. 301-302