Sri Aurobindo
Letters on Yoga
5. Planes and Parts of the Being
Each plane of our being – mental, vital, physical – has its own consciousness, separate though interconnected and interacting; but to our outer mind and sense, in our waking experience, they are all confused together. The body, for instance, has its own consciousness and acts from it, even without any mental will of our own or even against that will, and our surface mind knows very little about this body-consciousness, feels it only in an imperfect way, sees only its results and has the greatest difficulty in finding out their causes. It is part of the yoga to become aware of this separate consciousness of the body, to see and feel its movements and the forces that act upon it from inside or outside and to learn how to control and direct it even in its most hidden and (to us) subconscient processes. But the body-consciousness itself is only part of the individualised physical consciousness in us which we gather and build out of the secretly conscious forces of universal physical Nature.
There is the universal physical consciousness of Nature and there is our own which is a part of it, moved by it, and used by the central being for the support of its expression in the physical world and for a direct dealing with all these external objects and movements and forces. This physical consciousness-plane receives from the other planes their powers and influences and makes formations of them in its own province. Therefore we have a physical mind as well as a vital mind and the mind proper; we have a vital-physical part in us – the nervous being – as well as the vital proper; and both are largely conditioned by the gross material bodily part which is almost entirely subconscient to our experience.
The physical mind is that which is fixed on physical objects and happenings, sees and understands these only, and deals with them according to their own nature, but can with difficulty respond to the higher forces. Left to itself, it is sceptical of the 
existence of supraphysical things, of which it has no direct experience and to which it can find no clue; even when it has spiritual experiences, it forgets them easily, loses the impression and result and finds it difficult to believe. To enlighten the physical mind by the consciousness of the higher spiritual and supramental planes is one object of this yoga, just as to enlighten it by the power of the higher vital and higher mental elements of the being is the greatest part of human self-development, civilisation and culture.
The vital physical, on the other hand, is the vehicle of the nervous responses of our physical nature; it is the field and instrument of the smaller sensations, desires, reactions of all kinds to the impacts of the outer physical and gross material life. This vital physical part (supported by the lowest part of the vital proper) is therefore the agent of most of the lesser movements of our external life; its habitual reactions and obstinate pettinesses are the chief stumbling-block in the way of transformation of the outer consciousness by the yoga. It is also largely responsible for most of the suffering and disease of mind or body to which the physical being is subject in Nature.
As to the gross material part, it is not necessary to specify its place, for that is obvious; but it must be remembered that this too has a consciousness of its own, the obscure consciousness proper to the limbs, cells, tissues, glands, organs. To make this obscurity luminous and directly instrumental to the higher planes and to the divine movement is what we mean in our yoga by making the body conscious,– that is to say, full of a true, awake and responsive awareness instead of its own obscure, limited half-subconscience.
There is an inner as well as an outer consciousness all through our being, upon all its levels. The ordinary man is aware only of his surface self and quite unaware of all that is concealed by the surface. And yet what is on the surface, what we know or think we know of ourselves and even believe that that is all we are, is only a small part of our being and by far the larger part of us is below the surface. Or, more accurately, it is behind the frontal consciousness, behind the veil, occult and known only by an occult knowledge. Modern psychology and psychic 
science have begun to perceive this truth just a little. Materialistic psychology calls this hidden part the Inconscient, although practically admitting that it is far greater, more powerful and profound than the surface conscious self,– very much as the Upanishads called the superconscient in us the Sleep-self, although this Sleep-self is said to be an infinitely greater Intelligence, omniscient, omnipotent, Prajna, the Ishwara. Psychic science calls this hidden consciousness the subliminal self, and here too it is seen that this subliminal self has more powers, more knowledge, a freer field of movement than the smaller self that is on the surface. But the truth is that all this that is behind, this sea of which our waking consciousness is only a wave or series of waves, cannot be described by any one term, for it is very complex. Part of it is subconscient, lower than our waking consciousness, part of it is on a level with it but behind and much larger than it; part is above and superconscient to us. What we call our mind is only an outer mind, a surface mental action, instrumental for the partial expression of a larger mind behind of which we are not ordinarily aware and can only know by going inside ourselves. So too what we know of the vital in us is only the outer vital, a surface activity partially expressing a larger secret vital which we can only know by going within. Equally, what we call our physical being is only a visible projection of a greater and subtler invisible physical consciousness which is much more complex, much more aware, much wider in its receptiveness, much more open and plastic and free.
If you understand and experience this truth, then only you will be able to realise what is meant by the inner mental, the inner vital, the inner physical consciousness. But it must be noted that this term “inner” is used in two different senses. Sometimes it denotes the consciousness behind the veil of the outer being, the mental or vital or physical within, which is in direct touch with the universal mind, the universal life-forces, the universal physical forces. Sometimes, on the other hand, we mean an inmost mental, vital, physical, more specifically called the true mind, the true vital, the true physical consciousness which is nearer to the soul and can most easily and directly respond to the Divine Light and Power. There is no real yoga possible, still less 
any integral yoga, if we do not go back from the outer self and become aware of all this inner being and inner nature. For then alone can we break the limitations of the ignorant external self which receives consciously only the outer touches and knows things indirectly through the outer mind and senses, and become directly aware of the universal consciousness and the universal forces that play through us and around us. And then only too can we hope to be directly aware of the Divine in us and directly in touch with the Divine Light and the Divine Force. Otherwise we can feel the Divine only through external signs and external results and that is a difficult and uncertain way and very occasional and inconstant, and it leads only to belief and not to knowledge, not to the direct consciousness and awareness of the constant presence.
As for instances of the difference, I may give you two from the opposite poles of experience, one from the most external phenomena showing how the inward opens to the awareness of the universal forces, one of spiritual experience indicating how the inward opens to the Divine. Take illness. If we live only in the outward physical consciousness, we do not usually know that we are going to be ill until the symptoms of the malady declare themselves in the body. But if we develop the inward physical consciousness, we become aware of a subtle environmental physical atmosphere and can feel the forces of illness coming towards us through it, feel them even at a distance and, if we have learnt how to do it, we can stop them by the will or otherwise. We sense too around us a vital physical or nervous envelope which radiates from the body and protects it, and we can feel the adverse forces trying to break through it and can interfere, stop them or reinforce the nervous envelope. Or we can feel the symptoms of illness, fever or cold, for instance, in the subtle physical sheath before they are manifest in the gross body and destroy them there, preventing them from manifesting in the body. Take now the call for the Divine Power, Light, Ananda. If we live only in the outward physical consciousness, it may descend and work behind the veil, but we shall feel nothing and only see certain results after a long time. Or at most we feel a certain clarity and peace in the mind, a joy in the vital a happy state in the physical 
and infer the touch of the Divine. But if we are awake in the physical, we shall feel the light, power or Ananda flowing through the body, the limbs, nerves, blood, breath and, through the subtle body, affecting the most material cells and making them conscious and blissful and we shall sense directly the Divine Power and Presence. These are only two instances out of a thousand that are possible and can be constantly experienced by the sadhak.
Current publication:
Sri Aurobindo. Letters on Yoga // SABCL.- Volume 22. (≈ 28 vol. of CWSA).- Pondicherry: Sri Aurobindo Ashram, 1971.- 502 p.
Other publications:
1. 10161.
Sri Aurobindo. Letters on Yoga. I // CWSA.- Volume 28. (≈ 22 vol. of SABCL).- Pondicherry: Sri Aurobindo Ashram, 2012.- 590 p.
2. 20453.
Sri Aurobindo. Letters of Sri Aurobindo: In 4 Series.- First Series [On Yoga].- Bombay: Sri Aurobindo Circle, 1947.- 416 p.