between any two bodies would at once disturb the equilibrium existing between them and other bodies, and so tend to produce an unending series of readjustments. Furthermore, equalization with respect to any one quality or tendency does not mean equalization with respect to all. We have thus a twofold source of variation, and the conception of eternal change becomes at once less impossible than the conception of eternal rest. In addition, the doctrine of the dissipation of energy involves a fatal contradiction. If the world be running down by the conversion of all available energy into heat, how comes it about that the universe is at the same time cooling off by the loss of heat? The answer that the heat energy is being transferred to the ether is not satisfying, and it is particularly unsatisfying if one does not believe in the ether. An examination of the phenomena would lead one to the very contrary conclusion—that the world machine is not running down and that the universe is not cooling off.
The third book, on phenomenology, starts out with the denial of "force" and "energy" as separate physical entities, and seeks to find an explanation of acceleration and retardation, heat and molecular reaction, electricity and magnetism, conduction and induction, in terms of persistence, resistance, reciprocity, and equalization. Energy is regarded not as a cause of phenomena, but as a result, while "force" is dismissed as a metaphysical pitfall which has already claimed too many victims. The attempt is necessarily somewhat lengthy (it occupies two hundred pages), and the more so since the milk of human kindness in these two writers has not yet been condensed, but in the main it is a very successful attempt. It proceeds upon the true scientific principle—the search for similarities rather than for differences.
The same book also takes up the much-discussed question of action at a distance. We all remember Newton's words: "That gravitation should be innate, inherent, and essential to matter, so that one body may act on another at a distance through a vacuum without the mediation of anything else, by and through which their action and force may be conveyed from one to another, is to me so great an absurdity that I believe no man who in philosophical matters has a competent faculty of thinking can ever fall into it." But experience shows that equalization between two bodies in different states of excitation takes place the more readily in proportion as the intervening resistance is less. It is a natural inference, therefore, that the very most favorable condition for such equalization would be the absence of all resistance—that is, the absence of any intervening medium. Experiments with vacuum tubes confirm this inference. The more perfect the exhaustion the more perfect the transmission; and this is true not only of heat, light, and electricity, but as well of gravity itself,
