“In Sanskrit, the causal body is known as the Karana Sharira, Karana meaning cause. Briefly, the causal body has two main functions:
(1) To act as a vehicle for the ego: the causal body is the “body of Manas,” the form aspect of the individual, the true man, the Thinker.
(2) To act as a receptacle or storehouse for the essence of man’s experiences in his various incarnations. The causal body is that into which is woven everything which can endure, and in which are stored the germs of qualities, to be carried over to the next incarnation. Hence one sees that the lower manifestation of man, i.e., his expression in his mental, astral and physical bodies, depends ultimately upon the growth and development of the real man himself, the one “for whom the hour never strikes”.
At its inception, the causal body, or form-aspect of the true man, is described as a delicate film of subtlest matter, just visible, marking where the individual begins his separate life. That delicate, almost colourless, film of subtlest matter, is the body which will last through the whole of the human evolution: on this, as on a thread – the thread-self, or Sutratma, as it is sometimes called – will all the future incarnations be strung.
The causal body, as said, is the receptacle of all that is enduring – i.e., only that which is noble and harmonious, and in accordance with the law of the spirit; for every great and noble thought, every pure and lofty emotion, is carried up, and its essence worked into the substance of the causal body. Hence, the conditions of the causal body is a true register – the only true register – of the growth the man, of the stage of evolution to which he has attained. (…)
In the Thinker, residing in the causal body, are all the powers that we class as Mind, i.e., memory, intuition, will, the Thinker gathers up all experiences of the earth-lives, through which he passes, to be transmuted within himself, by his own divine alchemy, into that essence of experience and knowledge which is Wisdom. Even in the one brief earth-life we distinguish between the knowledge we acquire and the wisdom we gradually – often too rarely – distil from that knowledge. Wisdom is the fruitage of life’s experience, the crowning possession of the aged. In a much fuller and richer sense, Wisdom is the fruitage of many incarnations, the produce of much experience and knowledge. In the Thinker, thus, is the store of experiences, reaped in all his past lives, harvested through many rebirths.
In ordinary people the causal body is not yet fully active, and consequently only that matter which belongs to the third sub-plane is vivified. As the ego, during the long course of his evolution, unfolds his latent possibilities, the higher matter is gradually brought into activity; but it is only in the perfected men whom we call Adepts, or Masters, that it is developed to its fuller extent.
It is difficult to describe a causal body fully, because the senses belonging to the causal world are altogether different from and higher than those we employ at the physical level. Such memory of the appearance of a causal body, as it is possible for a clairvoyant to bring into his physical brain, represents it as an ovoid, that being, in fact, the shape of all the bodies, and as surrounding the physical body of the man, extending to a distance of about 18 inches from the surface of the physical body.
A human being, who has just individualised from the animal kingdom, has a causal body of a minimum size.
In the case of a primitive man, the causal body resembles a bubble and gives the impression of being empty. It is a mere colourless film, just sufficient, apparently, to hold itself together and make a reincarnating entity, but no more. Although it is filled with higher mental matter, this is not yet brought into activity, and so remains colourless and transparent. As the man develops, this matter is gradually stirred into alertness by vibrations which reach it from the lower bodies. This comes but slowly, because the activities of man in the earlier stages of his evolution are not of a character to obtain expression in matter so fine as that of the causal body. But when a man reaches the stage where he is capable either of abstract thought, or of unselfish emotion, the matter of the causal body is aroused into response.
The vibrations thus aroused show themselves in the causal body as colours, so that, instead of being a mere transparent bubble, it gradually becomes a sphere filled with matter of the most lovely and delicate hues, an object beautiful beyond all conception.
In the case of spiritually developed man, an enormous change is noticed. The glorious iridescent film is now completely filled with the most lovely colours, typifying the higher form of love, devotion and symphathy, aided by an intellect refined and spiritualised, and by aspirations reaching ever towards the divine. Some of these colours have no place in the physical plane spectrum.
The inconceivably fine and delicate matter of such a causal body is intensively alive, and pulsating with living fire, forming a radiant globe of flashing colours, its high vibrations sending ripples of changing hues over its surface – hues of which earth knows nothing – brilliant, soft and luminous beyond the power of language to describe. Such a causal body is filled with living fire, drawn from a still higher plane, with which it appears to be connected by a quivering thread of intense light.
Furthermore, from the upper part of the causal body there ascends a crown of brilliant sparks, indicating the activity of spiritual aspiration, and of course adding very greatly to the beauty and dignity of the man’s appearance. (…)
This very upward rushing of spiritual aspiration, which makes so glorious a crown for the developed man, is itself the channel through which the divine power descends: so that the fuller and stronger his aspiration become, the larger is the measure of the grace from on high.” (Geoffrey Hodson. Basic Theosophy, pp. 21-25; emphasis added)