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change? Now it is solar force, and now terrestrial; now sensible 
in masses, now latent and atomic ; now a wave of light, and now 
of sound; now buried deep in the earth, and now vanishing in 
the infinite azure of heaven. What other power compels the 
blind Titan to weary itself in these ceaseless transmigrations ? 
We can easily conceive one body, endowed with active power, 
pushing or pulling, seeking or avoiding, another. But how can 
we conceive a particle of motion, which is not a thing that 
moves, but an abstract quality or relation, pushing or pulling 
another particle of the same force? And even were this con- 
ceivable, since our total includes all the force in the universe, 
what other force can remain by which this blind Samson of 
modern speculation is compelled to grind for ever in his dreary 
prison-house? 
A last contradiction remains. The Indestructibility of Force, 
in its only definite sense, depends on our forming or conceiving 
a vast total of Potential Energies. This total consists of as 
many elements as there are pairs of atoms in the universe. 
Each element, again, can only he calculated by conceiving all 
the rest of the universe cancelled and destroyed*, and that pair 
of atoms to exist and act alone. As each partial Energy can 
only be conceived and reckoned under this hypothesis, so it can 
have no real existence, unless this conception is restored. The 
theory, as taught by Mr. Spencer, thus involves an almost 
infinite amount of self-contradiction. It affirms, first, that the 
total quantity of matter in the universe cannot be conceived as 
diminished, any more than conceived to be increased (F. Pr., 
p. 143). Next, it affirms as a twin doctrine, a primary truth, 
transcending demonstration, the fixed, invariable constancy of 
the total Energy of the universe. Yet this constant total, for 
its very existence, requires not only the conceived, but the actual 
destruction of the whole universe, save two atoms, as many 
times repeated in each single moment as there are pairs of 
atoms in all its countless worlds. 
The Persistence of Force, it thus appears, is no grand apriori 
truth, anticipating experience, and transcending demonstration. 
In the form it assumes in Mr. Spencer’s work it condenses into 
one ambiguous phrase a dozen demonstrable errors and contra- 
dictions. The view in Dr. Tyndall’s address, that it is at once 
a result of modern induction, and an a priori truth, needs no 
refutation. One alternative clearly excludes the other. On 
the other hand, the conservation of Vis viva is neither a proved 
conclusion, from ample scientific induction, nor a self-evident 
and necessary truth. It is the consequence which results from 
a conceivable hypothesis on the forces of the universe, that all 
