BKS Iyengar writes
“In order to understand this simplicity of the consciousness and purity of the Self, one needs a matured knowledge (paripakva jnana). We go to educational institutions to acquire knowledge. But to learn yoga, the institution is not outside. You have to step into your own university within the body, the mind and the intelligence. The body is an educational centre. The intelligence is its chancellor and volition is its vice-chancellor. Here the intelligence cannot work unless it is ignited by volition. Volition is will power. In yoga terminology, it is called iccha sakti or prerana sakti. Will power has the strength to take a decision. Intelligence without volition is impotent. Intelligence and will power, both being dynamic in their own ways, approach each other and get ignited and electrified. When the mind and intelligence come closer to each other, intelligence becomes meek, because the mind – being tricky – makes the intelligence oscillate. Yoga creates a state of equilibrium by training the mind and will power so that the will power is sharpened and the mind is tamed. Then the intelligence shines out with clarity and purity and steps out of the shadow of either the will or the mind’.
 Iyengar BKS, Astadala Yogamala Volume 1 p.105 –107