r; 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 of self-motion;
and nature, to act, has no need of a mover, whose pretended essence would
hinder him from acting.

42.

Whence comes man? What is his origin? Did the first man spring, ready
formed, from the dust of the earth? Man appears, like all other beings, a
production of nature. Whence came the first stones, the first trees, the
first lions, the first elephants, the first ants, the first acorns? We
are incessantly told to acknowledge and revere the hand of God, of an
infinitely wise, intelligent and powerful maker, in so wonderful a work as
the human machine. I readily confess, that the human machine appears to me
surprising. But as man exists in nature, I