Sri Aurobindo
Letters of Sri Aurobindo
Volume I - Part 2
The Muladhara is the centre of the physical consciousness proper, and all below in the body is the sheer physical, which as it goes downward becomes increasingly subconscient, but the real seat of the subconscient is below the body as the real seat 
of the higher consciousness (superconscient) is above the body. At the same time, the subconscient can be felt anywhere, felt as something below the movement of the consciousness and, in a way, supporting it from beneath or else drawing the consciousness down towards itself. The subconscient is the main support of all habitual movements, especially the physical and lower vital movements. When something is thrown out of the vital or physical, it very usually goes down into the subconscient and remains there as if in seed and comes up again when it can. That is the reason why it is so difficult to get rid of habitual vital movements or to change the character; for, supported or refreshed from this source, preserved in this matrix your vital movements, even when suppressed or repressed, surge up again and recur. The action of the subconscient is irrational, mechanical, repetitive. It does not listen to reason or the mental will. It is only by bringing the higher light and force into it that it can change.