ideas of them; that we distinguish one from another; that we assign
them properties. Now, to see or feel an object, the object must act
upon our organs; this object cannot act upon us, without exciting
some motion in us; it cannot excite motion in us, if it be not in
motion itself. At the instant I see an object, my eyes are struck
by it; I can have no conception of light and vision, without motion,
communicated to my eye, from the luminous, extended, coloured body.
At the instant I smell something, my sense is irritated, or put in
motion, by the parts that exhale from the odoriferous body. At the
moment I hear a sound, the tympanum of my ear is struck by the air,
put in motion by a sonorous body, which would not act if it were not
in motion itself. Whence it evidently follows, that, without motion,
I can neither feel, see, distinguish, compare, judge, nor occupy my
thoughts upon any subject whatever.

We are taught, that _the essence of a thing is that from which all
its properties flow_. Now, it is evident, that all the properties
of bodies, of which we have ideas, are owing to motion, which alone
informs us of their existence, and gives us the first conceptions
of them. I cannot be informed of my own existence but by the motions
I experience in myself. I am therefore forced to conclude, that
motion is as essential to matter as extension, and that matter cannot
be conceived without it.

Should any person deny, that motion is essential and necessary to matter;
they cannot, at least, help acknowledging that bodies, which seem dead
and inert, produce motion of themselves, when placed in a fit situation
to act upon one another. For instance; phosphorus, when exposed to the
air, immediately takes fire. Meal and water, when mixed, ferment.
Thus dead matter begets motion of itself. Matter has then the power