he
nature of a material thing as stated above (Q. 84, A. 7), but as that
by which it understands.

Reply Obj. 3: The axiom, "whatever is the cause of a thing being
such, is still more so," is true of things that are of the same
order, for instance, of the same kind of cause; for example, we may
say that health is desirable on account of life, and therefore life
is more desirable still. But if we take things of different orders
the axiom is not true: for we may say that health is caused by
medicine, but it does not follow that medicine is more desirable than
health, for health belongs to the order of final causes, whereas
medicine belongs to the order of efficient causes. So of two things
belonging essentially to the order of the objects of knowledge, the
one which is the cause of the other being known, is the more known,
as principles are more known than conclusions. But habit as such does
not belong to the order of objects of knowledge; nor are things known
on account of the habit, as on account of an object known, but as on
account of a disposition or form whereby the subject knows: and
therefore the argument does not prove.
_______________________

THIRD ARTICLE [I, Q. 87, Art. 3]

Whether Our Intellect Knows Its Own Act?

Objection 1: It would seem that our intellect does not know its own
act. For what is known is the object of the knowing faculty. But the
act differs from the object. Therefore the intellect does not know
its own act.

Obj. 2: Further, whatever is known is known by some act. If, then,
the intellect knows its own act, it knows it by some act, and again
it knows that act by some other act; this is to proceed indefinitely,
which seems impossible.

Obj. 3: Further, the intellect has the same relation to its act as
sense has to its act. But the proper sense does not feel its own act,
for this belongs to the common sense, as stated _De Anima_ iii, 2.
Therefore neither does the intellect understand its own act.

_On the contrary,_ Augustine says (De Trin. x, 11), "I understand
that I understand."

_I answer that,_ As stated above (AA. 1, 2) a thing is intelligible
according as it is in act. Now the ultimate perfection of the
intellect consists in its own operation: for this is not an act
tending to something else in which lies the perfection of the work
accomplished, as building is the perfection of the thing built; but
it remains in the agent as its perfection and act, as is said
_Metaph._ ix