The question is really as follows: How is it that for many a thinker — as experience teaches us — it is so exceedingly difficult to come to the point of being clairvoyant? This is connected with an important fact. What we call power of discrimination, power of judgment in man, in other words the logical thinking of the thinker, brings about a definite change in the whole structure of the human brain. Clear thinking causes a change in the physical instrument of the brain. Scientific research knows little of this, but it is a fact that a physical brain that has been used by a thinker has a different appearance from the brain which belongs to a non-thinker. The fact of being clairvoyant does not change it much. The brain of a non-thinker has very complicated convolutions, but that of a clear thinker is comparatively simple, without any special complications. Thinking actually expresses itself in the simplification of the convolutions of the brain. Present-day research knows nothing of this. Clear thinking is thinking that can survey wide vistas, not the thinking that occupies itself with analysis. Hence the greater simplicity of the brain-convolutions of a clear thinker. Whenever scientific research does condescend in any way to test clear thinking in its connection with material conditions, then it very soon appears that scientific research corroborates the statements of Spiritual Science.
The examination of the brain of Mendeleeff to whom science owes the exposition of the periodic system of the elements confirms what Spiritual Science says. His brain-convolutions were simpler than usual. Within certain limits he had the power of comprehensive thinking, and physical examination bore out absolutely the truth of what I have said. — I do not mention this as being of any very special value but only by the way. — Thus, as I have said, a change comes about in the instrument, and this change must be brought about by the activity of thought itself.
To be continued
Source: Rudolf Steiner – GA 117 – The tasks and aims of spiritual science – Stuttgart, 13th November 1909
Translated by D. S. Osmond