Sri Aurobindo
Letters of Sri Aurobindo
Volume I - Part 2
Forces, movements are not really planes but lines of consciousness or force which you may feel in that way one over the other. The planes are planes of consciousness and its powers – in the 
mind there is a mind of Knowledge (higher mind), a mind of will (dynamic mind) and a mind of thought (intellect) which are one above the other and it is these you probably mean. They easily get covered when their forces come down into the ordinary mind – covered by the lower consciousness.