It is impossible for the soul to become similar to sense-objects (in
order to grasp them), by remaining pure. How indeed could a point
become similar to a line? The intelligible line itself could not become
conformed to the sense-line, any more than intelligible fire to the
sense-fire, or the intelligible man to the sense-man. Nature herself
which begets man could not be identical with the begotten man. The
isolated soul, even if she could grasp sense-objects, will finish by
applying herself to the intuition of intelligible objects, because,
having nothing by which to grasp the former, she will let them escape.
Indeed, when the soul perceives from far a visible object, although
only the form reaches her, nevertheless what first began by being for
her indivisible, finally constitutes a subject, whether it be color or
a figure, whose size is determined by the soul.
SENSATION DEPENDS ON THE SENSE-SHAPE, WHICH, LIKE TOOLS, IS
INTERMEDIATE.
The soul and the exterior object do not therefore suffice (to explain
sensation); for there would be nothing that suffers. There must
therefore be a third term that suffers, that is, which receives the
sense-form, or, shape. This third term must "sympathize," or, share
the passion of the exterior object, it must also experience the same
passion, and it must be of the same matter; and, on the other hand,
its passion must be known by another principle; last, passion must
keep something of the object which produces it, without however being
identical with it. The organ which suffers must therefore be of a
nature intermediary between the object which produces the passion
and the soul, between the sensible and the intelligible, and thus
play the part of a term intermediary between the two extremes, being
receptive on one side, making announcements on the other, and becoming
equally similar to both. The organ that is to become the instrument of
knowledge must be identical neither with the subject that knows, nor
with the object that is known. It must become similar to both of them;
to the exterior object because it suffers, and to the cognizing soul
because the passion which it experiences becomes a form. Speaking more
accurately, the sensations operate by the organs. This results from
the principle asserted above, that the soul isolated from the body can
grasp nothing in the sense-world. As used here, the word "organ" either
refers to the whole body, or to some part of the body fitted to fulfil
some particular function; as in the case of touch or sight. Likewise,
it is easy to see that tools of artisans play a part intermediary
between the mind which judges, and the object which is judged; and that
they serve to discover the properties of substances. For instance, a
(foot) rule, which is equally conformed to the idea of straightness
in the mind, and to the property of straightness in the wood, serves
the artisan's mind as intermediary to judge if the wood he works be
straight.