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greater a priori truth, which some would iustate like a divinity 
on the throne of the universe. 
Force, by the usual definition, involved in Newton’s first 
and second axioms, and accepted in all works of exact science, 
is that which produces or tends to produce or destroy motion. 
To this definition two objections have lately been made, but 
wholly groundless. The first is that change in the state of 
matter with respect to its rest or motion may be produced by 
other matter in motion without the intervention of any force. 
But this is a radical misconception. A moving body does not 
alter, and cannot be conceived to alter, the state of another, 
except by the intervention of force. When the force varies 
with the distance, the motion of course alters its amount. 
Thus there may be immense repulsion occasioned by impact or 
apparent contact. But assume the absence of attractive or 
repulsive force altogether, and the motion of one body will have 
no effect at all on any other. Again, it is said that the resist- 
ance of a support is obviously not a force, but a statical pressure. 
It is, however, obvious that it is a force, because it is a statical 
pressure. For this really answers to one half of the definition. 
A pressure is a force which tends to produce motion, without 
actually producing it, because it is met and balanced by another. 
Let us now begin with the postulate which the doctrine 
plainly requires, to assume a definite form. Let us conceive 
the universe to consist of atoms, finite in number, or else all 
our calculations and reasonings will fail, but inconceivably 
numerous, and acted on by no forces but of mutual attractions 
and repulsions, which lessen as the distances increase. Let us 
further take Force in its proper sense, just defined, on which 
the Principia and all trains of strict dynamical reasoning 
depend. Is the total of force, in such a universe, fixed, constant, 
and invariable ? It is one of the simplest truths of Dynamics 
that it varies continually, from hour to hour, from moment to 
moment. If attractive forces are in excess, it increases in a 
condensing system, and decreases with dilatation. With 
repulsive forces it is the reverse. But it never for a moment 
continues the same. Of Force properly so called, the doctrine 
is not true at all, but exactly reverses the real truth. 
But Force is the cause of motion, and the motion caused by 
it often borrows the name. Thus momentum, or the mass 
multiplied by the velocity, is viewed as a kind of variety of 
force, and Vis viva, or living force, is used to express the 
amount of motion, as measured by the product of the mass and 
the square of the velocity. Is the statement true of the Vis 
viva of a system, or the force iu this improper sense? On the 
