Indispensable as is such a training in reading by turning to past conceptions of man, it does not suffice to meet the present-day demands of a scientific understanding of the universe. For this, we need a 'technique' of reading that cannot be attained along these lines alone. Awareness of this fact led Rudolf Steiner to pursue his spiritual-scientific investigations and to communicate the results in such a way that they can be a 'school of reading' for those who study them.2 In point of fact we have already made use in this sense of one of the results of Rudolf Steiner's researches, for at the very beginning of this book his picture of the threefold psycho-physical organism of man was taken as the basis of our own investigations. The reason why the present remarks were not then included is that the relevant results of higher research were in that case of such a nature that, once known, they could be confirmed by the simplest kind of self-observation. The fact, however, remains that from the very beginning we have called upon one fully trained in reading, to help in deciphering certain facts of nature - in this case of human nature. A similar need, though now in an amplified form, arises at the present stage of our studies. And here, out of the wealth of knowledge conveyed by Rudolf Steiner from the realm of supersensible Imagination, it is his characterization of the four modifications of levity which will now give the guidance necessary for our own observation. Adopting the terminology chosen by him for the description of this sphere, we shall in future speak of it as of the 'Ether' pervading the universe (thus using this word also in its true and original meaning). Accordingly, we shall refer to its fourfold differentiation as to the four kinds of ether: Warmth-Ether, Light-Ether, Chemical Ether and Life-Ether. * * * (b) WARMTH