Whether the Soul Knows Bodies Through the Intellect?
Objection 1: It would seem that the soul does not know bodies through
the intellect. For Augustine says (Soliloq. ii, 4) that "bodies cannot
be understood by the intellect; nor indeed anything corporeal unless
it can be perceived by the senses." He says also (Gen. ad lit. xii,
24) that intellectual vision is of those things that are in the soul
by their essence. But such are not bodies. Therefore the soul cannot
know bodies through the intellect.
Obj. 2: Further, as sense is to the intelligible, so is the intellect
to the sensible. But the soul can by no means, through the senses,
understand spiritual things, which are intelligible. Therefore by no
means can it, through the intellect, know bodies, which are sensible.
Obj. 3: Further, the intellect is concerned with things that are
necessary and unchangeable. But all bodies are mobile and changeable.
Therefore the soul cannot know bodies through the intellect.
_On the contrary,_ Science is in the intellect. If, therefore, the
intellect does not know bodies, it follows that there is no science of
bodies; and thus perishes natural science, which treats of mobile
bodies.
_I answer that,_ It should be said in order to elucidate this
question, that the early philosophers, who inquired into the natures
of things, thought there was nothing in the world save bodies. And
because they observed that all bodies are mobile, and considered them
to be ever in a state of flux, they were of opinion that we can have
no certain knowledge of the true nature of things. For what is in a
continual state of flux, cannot be grasped with any degree of
certitude, for it passes away ere the mind can form a judgment
thereon: according to the saying of Heraclitus, that "it is not
possible twice to touch a drop of water in a passing torrent," as
the Philosopher relates (Metaph. iv, Did. iii, 5).
After these came Plato, who, wishing to save the certitude of our
knowledge of truth through the intellect, maintained that, besides
these things corporeal, there is another genus of beings, separate
from matter and movement, which beings he called species or
"ideas," by participation of which each one of these singular and
sensible things is said to be either a man, or a horse, or the like.
Wherefore he said that sciences and definitions, and whatever
appertains to the act of the intellect, are not referred to these
sensible bodies, but to those beings immaterial and separate: so
that according to this the soul does not understand these corporeal
things, but the separate species thereof.
Now this may be shown to be false for two reasons. First, because,
since those species are immaterial and immovable, knowledge of
movement and matter would be excluded from science (which knowledge
is proper to natural science), and likewise all demonstration through
moving and material causes. Secondly, because it seems ridiculous,
when we seek for knowledge of things which are to us manifest, to
introduce other beings, which cannot be the substance of those
others, since they differ from them essentially: so that granted that
we have a knowledge of those separate substances, we cannot for that
reason claim to form a judgment concerning these sensible things.
Now it seems that Plato strayed from the truth because, having
observed that all knowledge takes place through some kind of
similitude, he thought that the form of the thing known must of
necessity be in the knower in the same manner as in the thing known.
Then he observed that the form of the thing understood is in the
intellect under conditions of universality, immateriality, and
immobility: which is apparent from the very operation of the
intellect, whose act of understanding has a universal extension, and
is subject to a certain amount of necessity: for the mode of action
corresponds to the mode of the agent's form. Wherefore he concluded
that the things which we understand must have in themselves an
existence under the same conditions of immateriality and immobility.
But there is no necessity for this. For even in sensible things it is
to be observed that the form is otherwise in one sensible than in
another: for instance, whiteness may be of great intensity in one,
and of a less intensity in another: in one we find whiteness with
sweetness, in another without sweetness. In the same way the sensible
form is conditioned differently in the thing which is external to the
soul, and in the senses which receive the forms of sensible things
without receiving matter, such as the color of gold without receiving
gold. So also the intellect, according to its own mode, receives
under conditions of immateriality and immobility, the species of
material and mobile bodies: for the received is in the receiver
according to the mode of the receiver. We must conclude, therefore,
that through the intellect the soul knows bodies by a knowledge which
is immaterial, universal, and necessary.
Reply Obj. 1: These words of Augustine are to be understood as
referring to the medium of intellectual knowledge, and not to its
object. For the intellect knows bodies by understanding them, not
indeed through bodies, nor through material and corporeal species;
but through immaterial and intelligible species, which can be in the
soul by their own essence.
Reply Obj. 2: As Augustine says (De Civ. Dei xxii, 29), it is not
correct to say that as the sense knows only bodies so the intellect
knows only spiritual things; for it follows that God and the angels
would not know corporeal things. The reason of this diversity is that
the lower power does not extend to those things that belong to the
higher power; whereas the higher power operates in a more excellent
manner those things which belong to the lower power.
Reply Obj. 3: Every movement presupposes something immovable: for
when a change of quality occurs, the substance remains unmoved; and
when there is a change of substantial form, matter remains unmoved.
Moreover the various conditions of mutable things are themselves
immovable; for instance, though Socrates be not always sitting, yet
it is an immovable truth that whenever he does sit he remains in one
place. For this reason there is nothing to hinder our having an
immovable science of movable things.
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