It was Crookes's fate to open the road which has brought man to nature's lower border and even across it, although he himself was in search of her upper border. What he was denied, we are in a position to achieve to-day, provided we do not expect to succeed by methods similar to those of atomic physics, and do not look for similar results. To show that there is a fourth state of matter, rightly so called, which represents in actual fact the upper border of nature, and to point the way that leads to it and across it, is the purpose of this chapter. * From our previous comparison of the older conception of the four elementary conditions of nature with that now held of the three states of ponderable matter, we may expect that the fourth state will have something in common with heat. Heat is indeed the energy which transforms matter by carrying it from the solid to the liquid and gaseous states. Not so obvious is the fact that heat, apart from being an agent working at matter in this way, is the very essence underlying all material existence, out of which matter in its three ponderable states comes into being and into which it is capable of returning again. Such a conception of matter was naturally absent from the age of the Contra-Levitatem orientation of the human mind. To create this conception, a new Pro-Levitate orientation is required. Apart from producing liquefaction and vaporization, heat has also the property of acting on physical matter so that its volume increases. Both facts are linked together by science through the thermodynamic conception of heat. As this conception firmly blocks the road to the recognition of the role of heat as the fourth state of matter, our first task will be to determine our own standpoint with regard to it. Further obstacles on our way are the so-called Laws of Conservation, which state that no matter and no energy - which for present-day science have become one and the same thing - can ever disappear into 'nothing' or come into being out of 'nothing'. This idea, also, will therefore require our early attention.2 * In the light of our previous studies we shall not find it difficult to test the reality-value of the thermodynamic conception of heat.