ows itself by
its own essence. For Augustine says (De Trin. ix, 3), that "the mind
knows itself, because it is incorporeal."

Obj. 2: Further, both angels and human souls belong to the genus of
intellectual substance. But an angel understands itself by its own
essence. Therefore likewise does the human soul.

Obj. 3: Further, "in things void of matter, the intellect and that
which is understood are the same" (De Anima iii, 4). But the human
mind is void of matter, not being the act of a body as stated above
(Q. 76, A. 1). Therefore the intellect and its object are the same in
the human mind; and therefore the human mind understands itself by
its own essence.

_On the contrary,_ It is said (De Anima iii, 4) that "the intellect
understands itself in the same way as it understands other things."
But it understands other things, not by their essence, but by their
similitudes. Therefore it does not understand itself by its own
essence.

_I answer that,_ Everything is knowable so far as it is in act, and
not, so far as it is in potentiality (Metaph. ix, Did. viii, 9): for
a thing is a being, and is true, and therefore knowable, according as
it is actual. This is quite clear as regards sensible things, for the
eye does not see what is potentially, but what is actually colored.
In like manner it is clear that the intellect, so far as it knows
material things, does not know save what is in act: and hence it does
not know primary matter except as proportionate to form, as is stated
Phys. i, 7. Consequently immaterial substances are intelligible by
their own essence according as each one is actual by its own essence.

Therefore it is that the Essence of God, the pure and perfect act, is
simply and perfectly in itself intelligible; and hence God by His own
Essence knows Himself, and all other things also. The angelic essence
belongs, indeed, to the genus of intelligible things as _act,_ but
not as a _pure act,_ nor as a _complete act,_ and hence the angel's
act of intelligence is not completed by his essence. For although an
angel understands himself by his own essence, still he cannot
understand all other things by his own essence; for he knows things
other than himself by their likenesses. Now the human intellect is
only a potentiality in the genus of intelligible beings, just as
primary matter is a potentiality as regards sensible beings; and
hence it is called "possible" [*Possibilis--elsewhere in this
translation render