THE MIND AND ITS ASPECTS
The internal organ or mind has four aspects:
First: Manas, the cogitating or thinking faculty, which is usually almost entirely wasted, because uncontrolled; properly governed, it is a wonderful power.
Second: Buddhi, the will (sometimes called the intellect).
Third: Ahamkara, the self-conscious egotism (from Ah am).
Fourth: Chitta, the substance in and through which all the faculties act, the floor of the mind as it were; or the sea in which the various faculties are waves.
Yoga is the science by which we stop Chitta from assuming, or becoming transformed into, several faculties. As the reflection of the moon on the sea is broken or blurred by the waves, so is the reflection of the Atman, the true Self broken by the mental waves.
Only when the sea is stilled to mirror-like calmness, can the reflection of the moon be seen, and only when the “mind-stuff,” the Chitta is controlled to absolute calmness, is the Self to be recognised. (VTII. 39-40)