, for they have not that power of using or of refraining,
which seems to belong to the notion of habit: and therefore, properly
speaking, there can be no habits in them.

Reply Obj. 3: The sensitive appetite has an inborn aptitude to be
moved by the rational appetite, as stated in _De Anima_ iii, text.
57: but the rational powers of apprehension have an inborn aptitude
to receive from the sensitive powers. And therefore it is more
suitable that habits should be in the powers of sensitive appetite
than in the powers of sensitive apprehension, since in the powers of
sensitive appetite habits do not exist except according as they act
at the command of the reason. And yet even in the interior powers of
sensitive apprehension, we may admit of certain habits whereby man
has a facility of memory, thought or imagination: wherefore also the
Philosopher says (De Memor. et Remin. ii) that "custom conduces much
to a good memory": the reason of which is that these powers also are
moved to act at the command of the reason.

On the other hand the exterior apprehensive powers, as sight, hearing
and the like, are not susceptible of habits, but are ordained to
their fixed acts, according to the disposition of their nature, just
as the members of the body, for there are no habits in them, but
rather in the powers which command their movements.
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FOURTH ARTICLE [I-II, Q. 50, Art. 4]

Whether There Is Any Habit in the Intellect?

Objection 1: It would seem that there are no habits in the intellect.
For habits are in conformity with operations, as stated above (A. 1).
But the operations of man are common to soul and body, as stated in
_De Anima_ i, text. 64. Therefore also are habits. But the intellect
is not an act of the body (De Anima iii, text. 6). Therefore the
intellect is not the subject of a habit.

Obj. 2: Further, whatever is in a thing, is there according to the
mode of that in which it is. But that which is form without matter,
is act only: whereas what is composed of form and matter, has
potentiality and act at the same time. Therefore nothing at the same
time potential and actual can be in that which is form only, but only
in that which is composed of matter and form. Now the intellect is
form without matter. Therefore habit, which has potentiality at the
same time as act, being a sort of medium between the two, cannot be
in the intellect; but only in the _conjunction,_ which is composed of
soul