L. From the lowest species, we proceed to the next above, and enquire,
what is the nature of a living entity; what we are to understand by the
term living, and what is life? To this, we shall be answered from the
schools, that life is motion _ab intrinsico_, and that living, means that
which moves _ab intrinsico_; that is, its motion is produced by some
intrinsic faculty, or virtue, which it has within itself.
LI. This definition is incumbered with greater difficulties than the
antecedent ones. All the modern philosophers oppose it, although for
distinct and contrary reasons. Gassendo, father Maignan, and the other
atomists, attribute motion _ab intrinsico_ to atoms, from which dogma it
will follow, that motion _ab intrinsico_, is not distinctly peculiar to
living animals. The Cartesians are very positive in maintaining, that
nothing can give motion to itself, but that all motion in the universe,
proceeds from that impulse, which God in the beginning gave to matter,
which does, and ever will subsist, without being impaired or injured;
and that by virtue of that impulse, motion is communicated from one part
of matter to another; so that all which was before at rest, upon its
beginning to move, received its impulse from some other body which was in
motion before, and transferred its influence to that which was then at
rest; and either partly, or in the whole, gave it the power of beginning
to move; and they say further, that man, which is the only living
corporeal entity they admit, when he moves, cannot be properly said to
give motion to his members, but only directs their motion by his will, in
virtue of the power antecedently impressed by the impulse of other bodies
on the animal spirits.
LII. It cannot be denied, that this doctrine is terribly fortified, by
the celebrated maxim of Aristotle, which says, _that every thing that
moves, is set in motion by something else_: and although the followers
of the common opinion, explain this maxim, so as to render it not
incompatible with the definition they give of living entities, there
results from this explanation, the inconvenience, that it weakens the
principal force of the axiom which they avail themselves of to prove
the existence of a first mover, to stimulate a body at rest; for if
we suppose, that a living entity has the power of moving itself, we
cannot maintain the necessity of a divine influence to produce this
motion, without admitting at the same time, the existence of a first
mover in other respects, to be established. Thus it seems to me, that
the Cartesians can with some colour of reason pretend, that religion
is interested in understanding the axiom in all the rigour, which they
profess to understand it themselves.
LIII. But be it as it may, with respect to this difficulty, and all
others, which the moderns by virtue of their principles can oppose to the
doctrine of Aristotle; it is certain, that there may be very serious ones
urged against their definition of living entities. Heavy bodies move _ab
intrinsico_, and are not living entities. Fire moves _ab intrinsico_,
and is not a living entity. The fermentative motion also, according to
common physics, is understood to be _ab intrinsico_. And I have remarked
and proved in another part of this work, that what the Aristotelites say
of heavy bodies being moved by communicated impulse, in the form this
explanation is intelligible, is also applicable to the motion of living
entities.