Science, like philosophy, has sought to escape from the doctrine of perpetual flux by finding some permanent substratum amid changing phenomena. Chemistry seemed to satisfy this desire. It was found that fire, which appears to destroy, only transmutes: elements are recombined, but each atom that existed before combustion still exists when the process is completed. Accordingly it was supposed that atoms are indestructible, and that all change in the physical world consists merely in re-arrangement of persistent elements. This view prevailed until the discovery of radio-activity, when it was found that atoms could disintegrate.Nothing daunted, the physicists invented new and smaller units, called electrons and protons, out of which atoms were composed; and these units were supposed, for a few years, to have the indestructibility formerly attributed to atoms. Unfortunately, it seemed that protons and electrons could meet and explode, forming, not new matter, but a wave of energy spreading through the universe at the velocity of light. Energy had to replace matter as what is permanent. But energy, unlike matter, is not a refinement of the common-sense notion of a “thing”; it is merely a characteristic of physical processes. It might be fancifully identified with the Heraclitean Fire, but it is the burning, not what burns. “What burns” has disappeared from modern physics.

Passing from that small to the large, astronomy no longer allows us to regard the heavenly bodies as everlasting.

The doctrine of perpetual flux, as taught by Heraclitus, is painful, and science, as we have seen, can do nothing to refute it. One of the main ambitions of philosophers has been to revive hopes that science seemed to have killed. Philosophers, accordingly, have sought, with great persistence, for something not subject to the empire of Time.