It must be emphasised again and again, that when it is given out, spiritual science, can indeed be understood. It cannot be emphasised often enough that one need not be a clairvoyant to understand spiritual science. One must of course be clairvoyant to arrive at results, but once they are there, one need not be clairvoyant. Understanding of spiritual science must precede personal vision. Here one can say: the opposite path is correct to that which is correct in the physical-sensible world. In the physical-sensible world, we first have correct perceptions, then we pass over to a thoughtful consideration of these, and we then form our scientific judgments. This must be reversed in the ascent to the spiritual world. There, we must first develop ideas — we must make every effort to live into spiritual science objectively; otherwise we can never be certain that any observation we make in the spiritual world is interpreted by us in the right sense. Hence knowledge must precede vision, and this is what is so infinitely disagreeable to many; the fact that they have to study spiritual science. Many consider this an incomprehensible demand. For it is relatively easy to have perceptions; but to interpret them aright — for this it is necessary that one enters rightly, — objectively, selflessly — into spiritual science.
Source: Rudolf Steiner – GA 161 – Meditation and Concentration – Dornach, 27th March 1915