Sri Aurobindo
Letters of Sri Aurobindo
Volume I - Part 1
Certainly, the mind and the inner being are consciousness. For human beings who have not got deeper into themselves mind and consciousness are synonymous. Only when one becomes more aware of oneself by a growing consciousness, then one 
can see different degrees, kinds, powers of consciousness, mental, vital, physical, psychic, spiritual. The Divine has been described as Being-Consciousness-Ananda, even as a Consciousness (Chaitanya), as putting out a force or energy, Shakti, that creates worlds. The mind is a modified consciousness that puts forth a mental energy. But the Divine can stand back from his energy and observe it at its work, it can be the Witness Purusha watching the works of Prakriti. Even the mind can do that – a man can stand back in his mind-consciousness and watch the mental energy doing things, thinking, planning, etc.; all introspection is based upon that fact that one can so divide oneself into a consciousness that observes and an energy that acts. These are quite elementary things supposed to be known to everybody. Anybody can do that merely by a little practice; anybody who observes his own thoughts, feelings, actions has begun doing it already. In Yoga we make the division complete, that is all.