The Metaphysics of a Naturalist 
57 
life require the postulate of pure spontaneous energy. Again, 
let us enquire what phenomena are thought to require pure elas- 
ticity in the ether. They are phenomena of propagation, e. g., 
all ponderable substances transmit various vibrations at rates 
depending, among other things, on the elasticity of the substance. 
But the rate of propagation in the unfilled spaces’’ bears no 
relation to such elasticity. It is necessary to assume that the 
medium is perfectly elastic but is more or less modified by the 
admixture of an imperfectly elastic substance. Now we submit 
that upon a dynamic theory this difficulty disappears. We sub- 
stitute for density, resistance and for elasticity, spontaneity. 
Under certain conditions of interference or resistance, forces 
pass from antagonistic equilibrium to concordant phases. Resist- 
ance (the criterion of force) disappears and unconditioned energy 
appears. This energy has no such temporal limitations as force 
has, and the result is the same as is conceived in the case of a 
vibration in a perfectly elastic medium. 
It would be interesting to trace the application of a dynamic 
theory to inertia and allied problems, but we notice one other 
point. When two moving elastic bodies impinge, the bodies 
suffer an alteration of their course and pursue the new path with 
unaltered velocity. No force has been lost, nothing has been 
gained; yet the whole fate of the bodies is changed, and their 
relation to the environment Here is something from nothing — 
an unthinkable proposition. What is it that has produced the 
great change. Change of direction or position is a very real 
thing. It is unnecessary to take into account the molecular 
changes. Let the two bodies be molecules if preferred. Again, 
if a bell be struck by a hammer it gives forth a tone and the force 
is, let us say, all employed in the process. The tone will depend on 
the figure and structure of the bell. Whatever it is, it is a differ- 
ent form of force from the blow. All the force is returned, but 
what produces the change? The fact of change is the paramount 
one, yet it is unexplained. Force is transformed without loss 
and might be collected again; then what is the essence of the 
change? Our answer is that every change of force is a death 
of force. Force can only change by passing through its precon- 
dition — energy — and in passing t) rough it obeys new laws. 
That which physics would fain explain by an appeal to elasticity 
is better explained by the idea of pure energy. The natural 
