summa-contra-gentiles

CHAPTER XCVIII 299
they would pass from potentiality to act, and thus they
would be moved per se or accidentally. There is, therefore,
in them potentiality and act as regards intelligible being,
just as there is in the heavenly bodies as regards natural
being. For the matter of a heavenly body
is so perfected
by its form, that it does not remain in potentiality to other
forms : and in like manner the intellect of a separate substance
is
wholly perfected by intelligible forms, with respect
to its natural knowledge. On the other hand our possible
intellect is
proportionate to the corruptible bodies to which
it is united as a form : because it is made to have certain
intelligible forms actually in such a way that it remains in
to others. For this reason it is stated in De
potentiality
Causis^ that an intelligence is full of forms, since, to
wit, the whole potentiality of its intellect is
And perfected by
thus one separate substance is able
intelligible forms.
to understand another through these intelligible forms.
Someone, however, may think that, since a separate
substance is intelligible by its nature, there is no need to
assert that one is understood by another through intelligible
species, but that they understand one another by the very
essence of the substance understood. For it would seem
that the fact of a substance being understood through an
intelligible species is accidental to material substances,
from their not being actually intelligible through their
essence : wherefore it is necessary for them to be understood
through abstract intentions. Moreover this seems in
accord with the statement of the Philosopher who says
(11 Metaph.y that in separate substances there is no distinction
between matter, intellect, the act of understanding,
and the thing understood.
And yet
if this be granted
it involves not a few difficulties.
First, because the intellect in act is the thing understood in
act according to the teaching of Aristotle :' and it is difficult
to see how one separate substance is identified with another
when it understands it.
Again. Every agent or operator acts through its form,
^ Loc.cit. * ix. 5.
*
-^De Aninta'vf. 2, \. 12.