matter, by which bodies are diversely determined. Gravitation is nothing
more than a mode of moving--a tendency towards a centre: to speak
strictly, all motion is relative gravitation; since that which falls
relatively to us, rises, with relation to other bodies. From this it
follows, that every motion in our microcosm is the effect of
gravitation; seeing that there is not in the universe either top or
bottom, nor any absolute centre. It should appear, that the weight of
bodies depends on their configuration, as well external as internal,
which gives them that form of action which is called gravitation. Thus,
for instance, a piece of lead, spherically formed, falls quickly and
direct: reduce this ball into very thin plates, it will be sustained in
the air for a much longer time: apply to it the action of fire, this
lead will rise in the atmosphere: here, then, the same metal, variously
modified, has very different modes of action.

A very simple observation would have sufficed to make the philosophers,
antecedent to Newton, feel the inadequateness of the causes they
admitted to operate with such powerful effect. They had a sufficiency to
convince themselves, in the collision of two bodies, which they could
contemplate, and in the known laws of that motion, which these always
communicate by reason of their greater or less compactness; from whence
they ought to have inferred, that the density of _subtle_ or _ethereal_
matter, being considerably less than that of the planets, it could only
communicate to them a very feeble motion, quite insufficient to produce
that velocity of action, of which they could not possibly avoid being
the witnesses.

If Nature had been viewed uninfluenced by prejudice, they must have been
long since convinced that matter acts by its own peculiar activity; that
it needs no exterior communicative force to set it in motion. They might