The turmoil of mental (intellectual) activity has also to be silenced like the vital activity of desire in order that the calm and peace may be complete. Knowledge has to come but from above. In this calm the ordinary mental activities like the ordinary vital activities become surface movements with which the silent inner self is not connected. It is the liberation necessary in order that the true knowledge and the true life-activity may replace or transform the activities of the Ignorance.
Ref : Letters on Yoga Vol. IV