summa-contra-gentiles

294 THE SUMMA CONTRA GENTILES
CHAPTER XCVni
HOW ONE SEPARATE SUBSTANCE UNDERSTANDS ANOTHER
If separate substances understand things that are by themselves
intelligible, as we have proved;^ and if
separate
substances are by themselves intelligible, since freedom
from matter makes a thing intelligible by itself, as appears
from the foregoing,^ it follows that separate substances
understand separate substances as their proper objects.
Wherefore each of them knows itself and others.
Each one indeed knows itself otherwise than the possible
intellect knows itself. For the possible intellect is in potentiality
in intelligible being, and is made actual by the
intelligible species, even as primary matter is made actual
in sensible being by a natural form. Now nothing is
known according as it is only in potentiality, but a thing
is known according as it is in act; hence the form is the
principle whereby we know the thing which is made actual
thereby, and in like manner the cognitive power
is made
actually cognizant by some species. Accordingly our
intellect does not know itself except by the species whereby
it is made actual in intelligible being; for which reason
Aristotle (3 De AnimaY says that it is knowahle in the same
way as other things, namely by species derived from phantasms,
as by their proper forms. On the other hand separate
substances, by their nature, exist actually in intelligible
being. Wherefore each one of them knows itself by its
essence, and not by the species of another thing. Since,
however, all knowledge is according as the image of the
thing known is in the knower ;
and since one separate
substance is like another as regards the common generic
nature, while they differ the one from the other in regard to
the species, as appears from the foregoing ;* it would seem
to follow that the one does not know the other,
» Ch. xcvi.
«
Ch. Ixxxii ;
Bk. I., ch. xliv.
• iv. 12. * Chs. xciii., xcv.
as regards