Sri Aurobindo
Letters of Sri Aurobindo
Volume IV - Part 3
It is good. Emptiness and silence of the consciousness prepare the being to live within, with the outer consciousness only as a means of communication and action on the physical world instead of living in the external only.
As there is a superconscient (something above our present consciousness) above the head from which the higher consciousness comes down into the body, so there is also a subconscient (something below our consciousness) below the feet. Matter is under the control of this power, because it is that out of which it has been created – that is why matter seems to us to be quite unconscious. The material body is very much under the influence of this power for the same reason; it is why we are not conscious of what is going on in the body, for the most part. The outer consciousness goes down into this subconscient when we are asleep, and so it becomes unaware of what is going 
on in us when we are asleep except for a few dreams. Many of these dreams rise up from the subconscient and are made up of old memories, impressions etc. put together in an incoherent way. For the subconscient receives impressions of all we do or experience in our lives and keeps these impressions in it, sending up often fragments of them in sleep. It is a very important part of the being, but we can do nothing much with it by the conscious will. It is the higher Force working in us that in its natural course will open the subconscient to itself and bring down into it its control and light.