Secondly, the statements of “exact thinkers” are on no account to be despised. Where they have to be taken seriously, one who occupies himself with them will thoroughly feel and appreciate this seriousness. The writer of this book would not like to be taken for one who lightly disregards the enormous thought-labour which has been expended in determining the limits of the human intellect. This thought-labour cannot be put aside with a few phrases about “academic wisdom” and the like. In many cases it has its source in true striving after knowledge and in genuine discernment. Indeed, even more than this must be admitted; reasons have been brought forward to show that that knowledge which is to-day regarded as scientific cannot penetrate into supersensible worlds, and these reasons _are in a certain sense irrefutable_. Now it may appear strange to many people that the writer of this book admits this freely, and yet undertakes to make statements about supersensible worlds. It seems indeed almost impossible that a person should admit _in a certain sense_ the reasons why knowledge of superphysical worlds is unattainable, and should yet speak about those worlds. Yet it is possible to take this attitude, and at the same time to understand that it impresses others as being inconsistent. It is not given to every one to enter into the experiences we pass through when we approach supersensible realms with the human intellect. Then it turns out that intellectual proofs may certainly be irrefutable, and that _notwithstanding this_, they need not be decisive with regard to reality. Instead of all sorts of theoretical explanations, let us now try to make this comprehensible by a comparison. That comparisons are not in themselves proofs is readily admitted, but this does not prevent their often making intelligible what has to be expressed. Human understanding, as it works in everyday life and in ordinary science, is actually so constituted that it cannot penetrate into superphysical worlds. This may be proven beyond the possibility of denial. But this proof can have no more value for a certain kind of soul-life than the proof one would use in showing that man’s natural eye cannot, with its visual faculty, penetrate to the smallest cells of a living being, or to the constitution of far-off celestial bodies. Just as the assertion is true and demonstrable that the ordinary power of seeing does not penetrate as far as the cells, so also is the other assertion which maintains that ordinary knowledge cannot penetrate into supersensible worlds. And yet the proof that the ordinary power of vision has to stop short of the cells in no way excludes the investigation of cells. Why should the proof that the ordinary power of cognition has to stop short of supersensible worlds, decide anything against the possibility of investigating those worlds?