It almost always happens that the formulations of genius are exaggerated and form the basis of a pernicious orthodoxy, and it has certainly happened to relativity theory. Against a tide of exaggerated praise Whitehead, Larmor, and Bridgman, as well as some Continental astronomers, have debated the general assumption that the theory of relativity is adequate to its task, but those in whose hands the power of orthodoxy lies have not yet answered their criticisms in print. Neglect has always been the weapon by which orthodoxy has unknowingly hindered the advance of new ideas. But while this neglect is easy to understand, it is really remarkable that the postulates of relativity theory were not subjected to closer examination before it was made the basis of wide philosophical speculation. The experimental confirmation of Einstein’s law of gravitation does not guarantee his postulates, since Whitehead has reached a similar law (identical within the accuracy of the observations) from different assumptions. Einstein’s profound creative intuition and use of a difficult technique compel our deepest respect, but his work should never have been regarded as a _general_ theory of time and space. Not only does he neglect the question of irreversibility but it is very doubtful if periodic processes can be made to fit into his scheme, as has been pointed out by Russell and Bridgman during the last year. Probably Einstein himself has never regarded his theory as more than a stage in the attempt to create a still wider physical synthesis, and we must not interpret in a broad sense his statement that one of the demands of his theory “takes away from space and time the last remnant of physical objectivity”.[6] This could only be true if physical time shared the absolute symmetry of space, i.e. if physical processes were all reversible. But there are processes from which we can obtain an objective criterion of the direction of time, and hence time does retain an element of physical objectivity as distinct from the absolute symmetry of space. One of the most interesting features in the future of physics will be the explanation of the fact that Einstein reached a correct law from postulates of limited validity, and in this connection Whitehead’s alternative derivation may prove to be of importance. CHAPTER III _Time in Astronomy and Physics_