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structibility, or the Persistence of Force, and the Conservation 
of Energy. The first has been perhaps the most usual. But 
Professor Huxley and Mr. Spencer detected in it a serious 
defect. Conservation seems to imply a Preserver, and an act 
of conserving. But this jars on the instincts of the new school 
of materialism, and contradicts its doctrine of the Unknowable 
They propose, then, the Persistence of Force as a better name. 
But their object is hardly attained. Language is obstinate, 
and brings in moral ideas, in spite of the most careful efforts 
to exclude them. Persistence, as the dictionaries tell us, means 
“ perseverance in a good or evil course, usually in one injurious,” 
“ obstinacy or contumacy.” It naturally implies a persevering 
action in spite of remonstrance or opposition. If the phrase, 
then, gets rid of the idea of a Preserver and Moral Governor, 
what does it introduce in its stead ? A deaf, blind Fate, which 
will persist in its course, heedless of all complaints from victims 
whom it tramples to death, or any attempted control by human or 
Divine intelligence. The idea it suggests is of the broomstick 
in the tale, that would persist in carrying buckets of water, till its 
owner’s house was deluged. He cut it in pieces, but the charm 
was strong in each fragment, and it carried the more. “ The 
mere machine saw and understood nothing. Insensible and 
without fatigue, it would have carried into his house the whole 
river.” But a higher power, gifted with reason, intei’posed. 
The charm was reversed, just in time to avert a great catastrophe, 
and the senseless, persistent thing persisted in its work no more. 
The other variation is still more important, and affects the 
essence and definition of the doctrine. This Titan of science, 
like Briareus in Homer, has two different names. It is Force 
with common mortals, but with analysts its name is Energy. 
And this is of two kinds, Kinetic and Potential. The conserva- 
tion is of their sum, and is a privilege which belongs to neither 
of the two partners, but to the partnership alone. 
The Indestructibility of Force, its name with Dr. Tyndall, is 
a vague expression, and may mean three or four different 
things. First, the indestructibility or invariableness of Force 
Proper, as defined in Newton’s laws, and dynamical science. 
Secondly, that of Force impi’oper, that is, of motion or mo- 
mentum, measured either by the velocity or its square. It will 
then assert the constancy of the collective or total motion of the 
universe. Thirdly, it may be the constancy of a Potential 
function, depending on the laws of force, either actual or sup- 
posed. Lastly, it may mean the constancy neither of force nor 
motion, but of a sum formed from both by some rule or process 
of dynamical science. 
