ected in us by the mere impression
of some superior beings, as Plato held; but that the higher and more
noble agent which he calls the active intellect, of which we have
spoken above (Q. 79, AA. 3, 4) causes the phantasms received from the
senses to be actually intelligible, by a process of abstraction.

According to this opinion, then, on the part of the phantasms,
intellectual knowledge is caused by the senses. But since the
phantasms cannot of themselves affect the passive intellect, and
require to be made actually intelligible by the active intellect, it
cannot be said that sensible knowledge is the total and perfect cause
of intellectual knowledge, but rather that it is in a way the
material cause.

Reply Obj. 1: Those words of Augustine mean that we must not expect
the entire truth from the senses. For the light of the active
intellect is needed, through which we achieve the unchangeable truth
of changeable things, and discern things themselves from their
likeness.

Reply Obj. 2: In this passage Augustine speaks not of intellectual
but of imaginary knowledge. And since, according to the opinion of
Plato, the imagination has an operation which belongs to the soul
only, Augustine, in order to show that corporeal images are impressed
on the imagination, not by bodies but by the soul, uses the same
argument as Aristotle does in proving that the active intellect must
be separate, namely, because "the agent is more noble than the
patient." And without doubt, according to the above opinion, in the
imagination there must needs be not only a passive but also an active
power. But if we hold, according to the opinion of Aristotle, that
the action of the imagination is an action of the "composite," there
is no difficulty; because the sensible body is more noble than the
organ of the animal, in so far as it is compared to it as a being in
act to a being in potentiality; even as the object actually colored
is compared to the pupil which is potentially colored. It may,
however, be said, although the first impression of the imagination is
through the agency of the sensible, since "fancy is movement produced
in accordance with sensation" (De Anima iii, 3), that nevertheless
there is in man an operation which by synthesis and analysis forms
images of various things, even of things not perceived by the senses.
And Augustine's words may be taken in this sense.

Reply Obj. 3: Sensitive knowledge is not the entire cause of
intell