The soul uses the causal body for its tenure of life on the causal plane. Though life in the heaven-worlds of the lower mental plane has been glorious, it does eventually come to an end. The mental body in turn drops away and the soul’s life in its causal body begins. The personality consists of the physical, astral and the lower mental bodies while the individuality consists of the ego in the causal body. As leaves grow on a tree to last through spring, summer and autumn, so do personalities manifest in the individual to last through the life periods spent on the physical, astral and lower mental planes. Just as the leaves assimilate and pass on nutriment to the sap, which is eventually withdrawn into the parent-trunk, and then perishes so does the personality gather experience and passes it on to the parent-individuality eventually and perishing when its task is completed. All through the heaven-life, the personality of the last physical life is distinctly preserved. It is only when the consciousness is finally withdrawn into the causal body, that this feeling of personality is merged into the individuality and the soul for the first time since its descent into incarnation realises itself as the true and comparatively permanent ego. In the causal body, one needs no windows, which were formed by one’s own thoughts in the lower heavens, as the causal plane is one’s true home. The causal plane is the true and relatively permanent home of the ego. Here one is free from the limitations of the personality, and is simply the reincarnating entity.
Physical, astral and mental bodies exist for one human incarnation only. i.e., are distinctly mortal, the causal body persists throughout the whole of one’s evolution and is therefore relatively immortal. This is because in due course, when one has completed one’s evolution on the causal plane, life on the still higher planes starting with the buddhic plane begins and actually one loses the causal body. The causal plane provides materials to clothe abstract thoughts, the lower mental plane provides materials to clothe concrete thoughts and the astral plane provides materials for the clothing of desires. The causal body owes its name to the fact that in it reside the causes which manifest themselves as effects on the lower planes. For it is the experiences of past lives, stored in the causal body, which are the cause of the general attitude towards life and the actions undertaken. In Sanskrit, the causal body is known as the Karana Sharira, Karana meaning cause. The causal body has two main functions; one is to act as a vehicle for the ego and the second is to act as a storehouse for the essence of the experiences of the ego in its various incarnations. In the causal body are stored the seeds of qualities to be carried over to the next incarnation. Hence one observes that the lower manifestation of the ego i.e., its expression in its mental, astral and physical bodies depends ultimately upon development in the causal body. This in turn, is dependent on the experiences it gains during its manifestation in the lower planes.
Thus the object of the ego is to unfold its latent powers and this it does by putting itself down in successive personalities. At its inception, the causal body is described as a delicate film of subtlest matter. This delicate, almost colourless film is the body which will last through the whole evolution process. The causal body is the storehouse of all that is noble and harmonious and in accordance with the law of the spirit, every great and noble thought’s essence is worked into the substance of the causal body. Hence the condition of the causal body is a true barometer of the growth of the individual.
All the other bodies (physical, astral and mental) should be regarded as casings or vehicles, enabling the ego to function on that particular plane.
The article is taken from the book Life Beyond Death by Anil Sharma