Sri Aurobindo
Letters of Sri Aurobindo
Volume I - Part 2
By the Supermind is meant the full Truth-consciousness of the Divine Nature in which there can be no place for the principle of division and ignorance; it is always a full light and knowledge superior to all mental substance or mental movement. Between the 
Supermind and the human mind are a number of ranges, planes or layers of consciousness – one can regard it in various ways – in which the element or substance of mind and consequently its movements also become more and more illumined and powerful and wide. The Overmind is the highest of these ranges; it is full of lights and powers; but from the point of view of what is above it, it is the line of the soul’s turning away from the complete and indivisible knowledge and its descent towards the Ignorance. For although it draws from the Truth, it is here that begins the separation of aspects of the Truth, the forces and their working out as if they were independent truths and this is a process that ends, as one descends to ordinary Mind, Life and Matter, in a complete division, fragmentation, separation from the indivisible Truth above. There is no longer the essential, total, perfectly harmonising and unifying knowledge, or rather knowledge for ever harmonious because for ever one, which is the character of Supermind. In the Supermind mental divisions and oppositions cease, the problems created by our dividing and fragmenting mind disappear and Truth is seen as a luminous whole. In the Overmind there is not yet the actual fall into Ignorance, but the first step is taken which will make the fall inevitable.