These revolutions of thought as to the final picture do not cause the scientist to lose faith in his handiwork, for he is aware that the completed portion is growing steadily. Those who look over his shoulder and use the present partially developed picture for purposes outside science, do so at their own risk. The lack of finality of scientific theories would be a very serious limitation of our argument, if we had staked much on their permanence. The religious reader may well be content that I have not offered him a God revealed by the quantum theory, and therefore liable to be swept away in the next scientific revolution. It is not so much the particular form that scientific theories have now taken—the conclusions which we believe we have proved—as the movement of thought behind them that concerns the philosopher. Our eyes once opened, we may pass on to a yet newer outlook on the world, but we can never go back to the old outlook. If the scheme of philosophy which we now rear on the scientific advances of Einstein, Bohr, Rutherford and others is doomed to fall in the next thirty years, it is not to be laid to their charge that we have gone astray. Like the systems of Euclid, of Ptolemy, of Newton, which have served their turn, so the systems of Einstein and Heisenberg may give way to some fuller realisation of the world. But in each revolution of scientific thought new words are set to the old music, and that which has gone before is not destroyed but refocussed. Amid all our faulty attempts at expression the kernel of scientific truth steadily grows; and of this truth it may be said—The more it changes, the more it remains the same thing. [50] This difficulty is evidently connected with the dual entry of time into our experience to which I have so often referred. [Pg 355] INDEX A B C of physics, xiv, 88 A priori probability, 77, 244, 305 Absolute, 23, 56; past and future, 48, 57, 295; elsewhere, 49, 50; values, 288, 331; future perfect, 307 Absorption of light, 184, 186 Abstractions, 53 Accelerated frames of reference, 113 Acceleration, relativity of, 129 Action, 180, 241; atom of, 182 Actuality, 266, 319 Aether, nature of, 31 Aether-drag, 3 Age of the sun, 169 And, study of, 104 Anthropomorphic conception of deity, 282, 337, 341 Antisymmetrical properties of world, 236 Ape-like ancestors, 16, 81, 273 Apple (Newton’s), 111, 115 Arrow, Time’s, 69, 79, 88, 295 Astronomer Royal’s time, 36, 40 Atom, structure of, 1, 190, 199, 224 Atom of action, 182. See Quantum Atomicity, laws of, 236, 245 Averages, 300 Awareness, 16, 334 Background of pointer readings, 137, 255, 259, 268, 330, 339 Balance sheet, 33 Beats, 216 Beauty, 105, 267, 350 Becoming, 68, 87 Beginning of time, 83 Berkeley, Bishop, xii, 326 Beta () particle, 59 Bifurcation of the world, 236 Billiard ball atoms, 2, 259