be indivisible; how does it happen, that this soul has the faculty of
memory, or of forgetfulness; is capacitated to think successively, to
divide, to abstract, to combine, to extend its ideas, to retain them, or
to lose them? How can it cease to think? If forms appear divisible in
matter, it is only in considering them by abstraction, after the method,
of geometricians; but this divisibility of form exists not in Nature, in
which there is neither a point, an atom, nor form perfectly regular; it
must therefore be concluded, that the forms of matter are not less
indivisible than thought.

What has been said is sufficient to show the generation of sensations,
of perceptions, of ideas, with their association, or connection in the
brain: it will be seen that these various modifications are nothing more
than the consequence of successive impulses, which the exterior organs
transmit to the interior organ, which enjoys the faculty of thought,
that is to say, to feel in itself the different modifications it has
received, or to perceive the various ideas which it has generated; to
combine them, to separate them, to extend them, to abridge them, to
compare them, to renew them, &c. From whence it will be seen, that
thought is nothing more than the perception of certain modifications,
which the brain either gives to itself, or has received from exterior
objects.

Indeed, not only the interior organ perceives the modifications it
receives from without, but again it has the faculty of modifying itself;
of considering the changes which take place in it, the motion by which
it is agitated in its peculiar operations, from which it imbibes new
perceptions and new ideas. It is the exercise of this power to fall back
upon itself, that is called _reflection_.