ur spiritual motor, which has
nothing that is necessary to put it into motion. Return from your
useless excursions; come down from an imaginary into a real world; take
hold of second causes; leave to theologians their "First Cause," of
which nature has no need in order to produce all the effects which you
see.

XLI.--OTHER PROOFS THAT MOTION IS IN THE ESSENCE OF MATTER, AND THAT IT
IS NOT NECESSARY TO SUPPOSE A SPIRITUAL MOTOR.

It is but by the diversity of impressions or of effects which substances
or bodies make upon us, that we feel them, that we have perceptions and
ideas of them, that we distinguish them one from another, that we assign
to them peculiarities. Moreover, in order to perceive or to feel an
object, this object must act upon our organs; this object can not act
upon us without exciting some motion in us; it can not produce any
motion in us if it is not itself in motion. As soon as I see an object,
my eyes must be struck by it; I can not conceive of light and of vision
without a motion in the luminous, extended, and colored body which
communicates itself to my eye, or which acts upon my retina. As soon as
I smell a body, my olfactory nerve must be irritated or put into motion
by the parts exhaled from an odorous body. As soon as I hear a sound,
the tympanum of my ear must be struck by the air put in motion by a
sonorous body, which could not act if it was not moved of itself. From
which it follows, evidently, that without motion I can neither feel,
see, distinguish, compare, nor judge the body, nor even occupy my
thought with any matter whatever. It is said in the schools, that the
essence of a being is that from which flow all the properties of that
being. Now then, it is evident that all the properties of bodies or of
substances of which we have ideas, are due to the motion which alone
informs us of their existence, and gives us the first conceptions of it.
I can not be informed or assured of my own existence but by the motions
which I experience within myself. I am compelled to conclude that motion
is as essential to matter as its extension, and that it can not be
conceived of without it. If one persists in caviling about the evidences
which prove to us that motion is an essential property of matter, he
must at least acknowledge that substances which seemed dead or deprived
of all energy, take motion of themselves as soon as they are brought
within the proper distance to act upon each other. Py