51. We have already seen that the influence of the dark radiation has long since become a fundamental factor in mankind's manifestation and mental life as a natural capacity and aptitude and now begins to be undermined by the Creative Principle's light radiation. This undermining is constantly in progress, so the light radiation will at last be able to take over the position which the dark radiation possesses at present, and in the same way, as a natural faculty and aptitude, will become the fundamental factor in human beings' manifestations and experiences of life. But in order that this undermining can take place, the light radiation from the Creative Principle has to be clothed in that kind of energy or matter which can be comprehensible for human beings' sense perception. This means simply that it has to be transformed into thought pictures which are precisely so adjusted that they are neither too high nor too low in order to be suitable for their brain power. One has to remember here that the brain of the human being is responsive only to mental images of a certain specific intensity. Mental images which by nature are above this intensity become blurred, unrealistic and quite inaccessible to the individual, while mental images lying below that intensity are also blurred, becoming primitive and dissolving in naïvety. And so the Creative Principle's light radiation, in order to become accessible to people, has to be transformed into mental images of such a suitable intensity or "wavelength" as can tune in to their brain organs according to their development and experience. That kind of mental image in which the Creative Principle's light radiation is incarnated in our day is identical with what we call "religious thought". And where this religious thought is of such a nature that it forms independent systems, these systems can be recognized as identical with those which are expressed as "religions" and these split again into "religious sects" and "church or religious communities". As the individual's brain organ changes with development so that it is gradually able to take in mental images of greater and greater intensity, so it is also able to receive the Creative Principle's light radiation in correspondingly stronger and more refined forms of mental images. And thus we see too - as we have begun to explain in the Introduction - that mankind has little by little changed religions, or ways of faith, in that religions which had previously been fulfilling, stimulating and uplifting for individuals, gradually became outmoded or naïve, and new world concepts arose which later on in the same way became antiquated and primitive, and this continued in accordance with the extent to which people were able to take in mental images of a more radical and refined material or "wavelength".