urately proposes and demonstrates
the art of measuring. But since the manual arts are chiefly conversant
in the moving of bodies, it comes to pass that geometry is commonly
referred to their magnitudes, and mechanics to their motion. In this
sense rational mechanics will be the science of motions resulting
from any forces whatsoever, and of the forces required to produce any
motions, accurately proposed and demonstrated. This part of mechanics
was cultivated by the ancients in the five powers which relate to
manual arts, who considered gravity (it not being a manual power) no
otherwise than as it moved weights by those powers. Our design, not
respecting arts, but philosophy, and our subject, not manual, but
natural powers, we consider chiefly those things which relate to
gravity, levity, elastic force, the resistance of fluids, and the like
forces, whether attractive or impulsive; and therefore we offer this
work as mathematical principles of philosophy; for all the difficulty
of philosophy seems to consist in this--from the phenomena of motions
to investigate the forces of nature, and then from these forces
to demonstrate the other phenomena; and to this end the general
propositions in the first and second book are directed. In the third
book we give an example of this in the explication of the system of
the World; for by the propositions mathematically demonstrated in the
first book, we there derive from the celestial phenomena the forces
of gravity with which bodies tend to the sun and the several planets.
Then, from these forces, by other propositions which are also
mathematical, we deduce the motions of the planets, the comets, the
moon, and the sea. I wish we could derive the rest of the phenomena of
nature by the same kind of reasoning from mechanical principles; for
I am induced by many reasons to suspect that they may all depend
upon certain forces by which the particles of bodies, by some causes
hitherto unknown, are either mutually impelled towards each other, and
cohere in regular figures, or are repelled and recede from each other;
which forces being unknown, philosophers have hitherto attempted the
search of nature in vain; but I hope the principles here laid
down will afford some light either to that or some truer method of
philosophy.
In the publication of this work, the most acute and universally
learned Mr. Edmund Halley not only assisted me with his pains in
correcting the press and taking care of t
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