Some of the terms used in Yoga are necessarily to be known. For Yoga takes man for a special purpose and studies him for a special end and, therefore, only troubles itself about two great facts regarding man, mind and body. First, he is a unit, a unit of consciousness. That is a point to be definitely grasped. There is only one of him in each set of envelopes, and sometimes the Theosophist has to revise his ideas about man when he begins this practical line. Theosophy quite usefully and rightly, for the understanding of the human constitution, divides man into many parts and pieces. We talk of physical, astral, mental, etc. Or we talk about Sthula-sarira, Sukshma-sarira, Karana-sarira, and so on. Sometimes we divide man into Anna-maya-kosa, Prana-maya-kosa, Mano-maya-kosa, etc. We divide man into so many pieces in order to study him thoroughly, that we can hardly find the man because of the pieces. This is, so to say, for the study of human anatomy and physiology.
But Yoga is practical and psychological. I am not complaining of the various sub-divisions of other systems. They are necessary for the purpose of those systems. But Yoga, for its practical purposes, considers man simply as a duality mind and body, a unit of consciousness in a set of envelopes. This is not the duality of the Self and the Not-Self. For in Yoga, "Self" includes consciousness plus such matter as it cannot distinguish from itself, and Not-Self is only the matter it can put aside.
Man is not pure Self, pure consciousness, Samvid. That is an abstraction. In the concrete universe there are always the Self and His sheaths, however tenuous the latter may be, so that a unit of consciousness is inseparable from matter, and a Jivatma, or Monad, is invariably consciousness plus matter.
In order that this may come out clearly, two terms are used in Yoga as constituting man Prana and Pradhana, life-breath and matter. Prana is not only the life-breath of the body, but the totality of the life forces of the universe or, in other words, the life-side of the universe.
"I am Prana," says Indra. Prana here means the totality of the life-forces. They are taken as consciousness, mind. Pradhana is the term used for matter. Body, or the opposite of mind, means for the yogi in practice so much of the appropriated matter of the outer world as he is able to put away from himself, to distinguish from his own consciousness.
This division is very significant and useful, if you can catch clearly hold of the root idea. Of course, looking at the thing from beginning to end, you will see Prana, the great Life, the great Self, always present in all, and you will see the envelopes, the bodies, the sheaths, present at the different stages, taking different forms; but from the standpoint of yogic practice, that is called Prana, or Self, with which the man identifies himself for the time, including every sheath of matter from which the man is unable to separate himself in consciousness. That unit, to the yogi, is the Self, so that it is a changing quantity. As he drops off one sheath after another and says: " That is not myself," he is coming nearer and nearer to his highest point, to consciousness in a single film, in a single atom of matter, a Monad. For all practical purposes of Yoga, the man, the working, conscious man, is so much of him as he cannot separate from the matter enclosing him, or with which he is connected. Only that is body which the man is able to put aside and say: "This is not I, but mine." We find we have a whole series of terms in Yoga which may be repeated over and over again. All the states of mind exist on every plane, says Vyasa, and this way of dealing with man enables the same significant words, as we shall see in a moment, to be used over and over again, with an ever subtler connotation; they all become relative, and are equally true at each stage of evolution.
Now it is quite clear that, so far as many of us are concerned, the physical body is the only thing of which we can say: " It is not myself "; so that, in the practice of Yoga at first, for you, all the words that would be used in it to describe the states of consciousness, the states of mind, would deal with the waking consciousness in the body as the lowest state, and, rising up from that, all the words would be relative terms, implying a distinct and recognisable state of the mind in relation to that which is the lowest. In order to know how you shall begin to apply to yourselves the various terms used to describe the states of mind, you must carefully analyse your own consciousness, and find out how much of it is really consciousness, and how much is matter so closely appropriated that you cannot separate it from yourself.