No one is born with all the faculties he will possess later; he may have tendencies in certain directions, but the faculties themselves he must first develop. So it is a fact that changes take place in the brain in the course of a man’s life. After a life of thought the instrument of thinking is different from what it was before.
Now the fact is that our etheric body, which for clairvoyant consciousness must be loosened from the physical brain, becomes more closely bound to the brain through the activity of thought. Thinking chains the etheric body firmly to the brain. If through his karma anyone has not yet the forces necessary to loosen it again at the right time, it may be that he cannot get far in clairvoyance in this incarnation; this depends on his karma. Supposing that in a former incarnation his karma had ordained him to be a clear thinker, then at the present time his thinking will not bind his etheric body so strongly to the brain; he will be able to set free his etheric body comparatively easily, and for the very reason that the elements of thought are the best preparation for ascending into the higher worlds — for this very reason he can investigate the secrets of the higher worlds in the most intimate way. Of course he must first set free again the etheric body from the brain. But if with what one may call the fine chiseling of thought the etheric body has become so caught in the physical brain that it is exhausted, then his karma may perhaps make him wait a long time before he can set it free again. When, however, the etheric body does become free, it will mean that he has passed the point of logical thought. Then what he has acquired can never be lost; no one can take it away from him. That is an essential and important fact, because otherwise clairvoyance can often be lost again after it has been acquired.
To be continued
Source: Rudolf Steiner – GA 117 – The tasks and aims of spiritual science – Stuttgart, 13th November 1909
Translated by D. S. Osmond