summa-contra-gentiles

CHAPTER CI 305
the intelligible species of which is actually in the intellect.
For since a substance which has understanding has also a
it is in
will, and consequently has the control of its action,
its power, when it
already has an intelligible species,
to make
use of it for understanding actually ; or, if it have several
species, to use one of them. Wherefore we do not actually
consider all the things whereof we possess knowledge.
Therefore an intellectual substance that has knowledge
through several species, uses one of them as it will, and
thereby knows actually at the same time all that he knows
by one species; for they are all as one intelligible thing in
so far as they are known through one (species), even as our
intellect knows at the same time several things compared
or related to one another as one individual thing. But it
does not know at the same time the things which it knows
through different species. Therefore as there is one understanding
so is there one thing actually understood.
Accordingly in the intellect of a separate substance there
is a certain succession of understandings : there is not,
however, movement properly speaking, since act does not
succeed potentiality, but act succeeds act. Whereas the
divine intellect, forasmuch as it knows all things through
one, namely the divine essence, and because its act is its
essence, knows all things at the same time. Consequently
there is no succession in His understanding, but His act
of intelligence is wholly perfect at the same time, and
endureth through all ages. Amen.