D O C . 3 1 3 O N C U R R E N T S T AT E O F F I E L D T H E O R Y 2 9 9 is (and how natural processes proceed), but rather we also want to achieve as far as possible the perhaps utopian and seemingly arrogant goal of knowing why Nature is thus and not otherwise. This area encompasses the highest degree of satisfaction for scientific thinkers. One can, for example, deduce from the molecular-kinetic theory of heat a certain quantitative relation between the pressure, volume, and temperature of a monatomic gas (equation of state) on the one hand, and its heat capacity on the other hand similarly, a quantitative relation between the viscosity and the thermal conductivity of such gases. In all such cases, the point is to interpret the empirical laws as logical necessities. If, to wit, one has accepted the fundamental hypothesis of the molecular-kinetic theory of heat, then one discovers, in a way,[4] that God himself could have not have ordered these interrelations in any other way than they in fact are no more than it would have been in His power to make the number 4 into a prime.1 This is the Promethean element in scientific experience that is con- tained in the academic expression “logical unity.” This has been for me the real magic of scientific reflection it is, so to speak, the religious basis of scientific en- deavor.— After this excursion, we return to field theory, whose next steps were aimed at logical unity. Out of the equivalence of all inertial systems, as observed experimen- tally, together with our empirical experience of the constancy of the velocity of light propagation, which found its most compact expression in the electrodynamics of Maxwell and Lorentz, the special theory of relativity was born. It brought us a considerable unification of previously independent theoretical concepts on the one hand the electric and the magnetic field, on the other inertial mass and energy were fused into a unified entity. These advances are also owing to field theory. The next step on the path to unification was the general theory of relativity. It combined into a logical unit the previously separate concepts of inertia and gravi- tation, which had long been connected on an empirical level by the notion of mass. Its greatest charm, however, consists in the fact that it—starting from quite general logical principles (the equivalence of all states of motion)—permitted a derivation of the complicated field law for gravitation in a logical way. This law was found as the answer to the question: What are the simplest laws that we can apply to a four- dimensional continuum that obeys a Riemannian metric? The success of this at- tempt to derive subtle laws of nature in a purely theoretical manner from a convic- tion of the formal simplicity of reality encourages us to proceed along this speculative path, whose dangers must be kept vividly in mind by all those who dare to tread along it.2 1 It should be self-evident that these sentences are not intended to convey an epistemological sa- gacity but rather only a certain experience of the scientific researcher. 2 Meyerson’s comparison with Hegel’s goal setting is certainly justified to some extent it illumi- nates most clearly the danger to be feared here.[5] [p. 127]