For most people, everything that takes place in the mind is simply mental activity. Psychology as a science in the West has only, in recent years, begun to appreciate there are different types of intelligence that, presumably, arise from different sources. The discussion of “left brain” and “right brain” focus, between the mathematical, ordered reason and the creative, artistic and expressive sides of the brain do not take this far enough to provide insight for a yogic practice that needs must gain mastery over all aspects of mental energy and the acquisition of knowledge and the implementation of that knowledge. Modern day researchers have begun to understand something of this with discussion of the source of the creative process, the differences between mental intelligence and emotional intelligence, and even things like “muscle memory” which implies a learned response that automatically activates the body to respond in certain situations.
Much effort has been put into distinguishing between various functions of mind, such as memory, reason, power of expression, creativity, and the more automatic functions that regulate the vital, nervous and physical systems of the body. Work has been done to distinguish between various neurotransmitters and their effects on the mind and body. Yet for the practitioner of yoga, this is just the beginning of the process of understanding that needs to take place to gain control over the endless stream of impulses, feelings, thoughts, perceptions, imaginations and conceptual development that takes place all the time, and which can (and do) distract the seeker from the path.
Sri Aurobindo observes: “The mind proper is divided into three parts — thinking Mind, dynamic Mind, externalising Mind — the former concerned with ideas and knowledge in their own right, the second with the putting out of mental forces for realisation of the idea, the third with the expression of them in life (not only by speech, but by any form it can give). The word ‘physical mind’ is rather ambiguous, because it can mean this externalising Mind and the mental in the physical taken together.”
“Vital Mind proper is a sort of a mediator between vital emotion, desire, impulsion, etc. and the mental proper. It expresses the desires, feelings, emotions, passions, ambitions, possessive and active tendencies of the vital and throws them into mental forms (the pure imaginations or dreams of greatness, happiness, etc. in which men indulge are one peculiar form of the vital-mind activity). There is still a lower stage of the mental in the vital which merely expresses the vital stuff without subjecting it to any play of intelligence. It is through this mental vital that the vital passions, impulses, desires rise up and get into the Buddhi and either cloud or distort it.”
“As the vital Mind is limited by the vital view and feeling of things (while the dynamic Intelligence is not, for it acts by the idea and reason), so the mind in the physical or mental physical is limited by the physical view and experience of things, it mentalises the experiences brought by the contacts of outward life and things and does not go beyond that (though it can do that much very cleverly), unlike the externalising mind which deals with them more from the reason and its higher intelligence. But in practice these two usually get mixed together. The mechanical mind is a much lower action of the mental physical which, left to itself, would only repeat customary ideas and record the natural reflexes of the physical consciousness to the contacts of outward life and things.”
Sri Aurobindo, Integral Yoga: Sri Aurobindo’s Teaching and Method of Practice, Planes of Consciousness and Parts of the Being, pp. 51-56