D O C . 1 5 6 O N B A S I C C O N C E P T S O F P H Y S I C S 1 6 3 Physics first took the concepts of number, space, time, and objects from pre- scientific thinking & attempted to make them suffice for its constructions. First the study of the spatial relations between objects without temporal evolution was cre- ated, Euclidean geometry. The creation of this first logical system of concepts, which relates to the spatial properties of material objects, is to the undying credit of the ancient Greeks. It was followed by the study of the spatial changes of bodies over time this was classical mechanics, founded by Galileo & Newton, which for its own part made use of Euclidean geometry as its basis. This theory was first of all created to explain the motions of the celestial bodies. Its fundamentals are the following: A pointlike body moves rectilinearly and uni- formly, provided that it is sufficiently far from all other bodies. If other bodies are sufficiently near, the given body will move with an acceleration that is completely determined by its position with respect to other bodies. In particular, the determi- nation of the acceleration from the positions of other bodies was possible by spe- cific hypotheses on the nature of forces between bodies. One of them was gravitation, whose complete mathematical description was given by Newton. This strictly causal scheme was, however, able to yield more than just an expla- nation of mechanical phenomena in the strict sense. Other changes in objects, which were not immediately identifiable as mechanical, such as changes in their aggregate state, their temperature, and chemical processes, could be thought of as motions & equilibria of their smallest constituents. This striving to reduce all ma- terial processes to mechanics led inevitably to the atomic theory.[4] Extensions of the hypotheses concerning the forces seemed to conceive of all processes as strictly causal and mechanical. This program, which was already presaged by the great materialist philosophers in ancient Greece, reads as follows: Reality consists only of pointlike masses that experience no changes except for motions that follow Newton’s rules. Applying this fundamental idea, marvelous results were obtained. Celestial me- chanics, technical mechanics, the theory of heat, the theory of crystals, and chem- istry developed on this basis without encountering difficulties of principle. Even the theories of electromagnetism & of light seemed at first to fit into this picture without contradictions. The existence of unchangeable elementary particles (elec- trons & protons) would seem to be assured today. And yet we now know with certainty that Newton’s fundamental concepts & hy- potheses are only an approximation to the true reality. It was at first the laws of electricity & of light that necessitated the coinage of new fundamental concepts. After the wave character of light became apparent in the first half of the nineteenth century, light propagation could in fact still be considered to be due to the motions of a hypothetical body, the luminous ether. But the more precisely the properties of light became known, the more difficult it became to ascribe mechanical properties [p. 3] [p. 4]