Sri Aurobindo
Letters of Sri Aurobindo
Volume I - Part 2
It is (sometimes directly, sometimes indirectly) by the power of the Overmind releasing the mind from its close partitions that the cosmic consciousness opens in the seeker and he becomes aware of the cosmic spirit and the play of the cosmic forces.
It is from or at least through the overmind plane that the original prearrangement of things in this world is effected; for from it the determining vibrations originally come. But there are corresponding movements on all the planes, the mind, the vital, the physical even, and it is possible in a very clear or illumined condition of the lower consciousness to become aware of these movements and understand the plan of things and be a conscious instrument or even, to a limited extent, a determinant Will or Force. But the stuff of the lower planes always mixes with the overmind forces and diminishes or even falsifies and perverts their truth and power.
It is even possible for the Overmind to transmit to the lower 
planes of consciousness something of the supramental Light; but, so long as the Supermind does not directly manifest, its Light is modified in Overmind itself and still further modified in the application by the needs, the demands, the circumscribing possibilities of the individual nature. The success of this diminished and modified Light, e.g. in purifying the physical, cannot be immediate and absolute as the full and direct supramental action would be; it is still relative, conditioned by the individual nature and the balance of the universal forces, resisted by adverse powers, baulked of its perfect result by the unwillingness of the lower workings to cease, limited either in its scope or in its efficacy by the want of a complete consent in the physical nature.