receives through the agent's action.
________________________

THIRD ARTICLE [I-II, Q. 52, Art. 3]

Whether Every Act Increases Its Habit?

Objection 1: It would seem that every act increases its habit. For
when the cause is increased the effect is increased. Now acts are
causes of habits, as stated above (Q. 51, A. 2). Therefore a habit
increases when its acts are multiplied.

Obj. 2: Further, of like things a like judgment should be formed. But
all the acts proceeding from one and the same habit are alike (Ethic.
ii, 1, 2). Therefore if some acts increase a habit, every act should
increase it.

Obj. 3: Further, like is increased by like. But any act is like the
habit whence it proceeds. Therefore every act increases the habit.

_On the contrary,_ Opposite effects do not result from the same
cause. But according to _Ethic._ ii, 2, some acts lessen the habit
whence they proceed, for instance if they be done carelessly.
Therefore it is not every act that increases a habit.

_I answer that,_ "Like acts cause like habits" (Ethic. ii, 1, 2). Now
things are like or unlike not only in respect of their qualities
being the same or various, but also in respect of the same or a
different mode of participation. For it is not only black that is
unlike white, but also less white is unlike more white, since there
is movement from less white to more white, even as from one opposite
to another, as stated in _Phys._ v, text. 52.

But since use of habits depends on the will, as was shown above (Q.
50, A. 5); just as one who has a habit may fail to use it or may act
contrary to it; so may he happen to use the habit by performing an
act that is not in proportion to the intensity of the habit.
Accordingly, if the intensity of the act correspond in proportion to
the intensity of the habit, or even surpass it, every such act either
increases the habit or disposes to an increase thereof, if we may
speak of the increase of habits as we do of the increase of an
animal. For not every morsel of food actually increases the animal's
size as neither does every drop of water hollow out the stone: but
the multiplication of food results at last in an increase of the
body. So, too, repeated acts cause a habit to grow. If, however, the
act falls short of the intensity of the habit, such an act does not
dispose to an increase of that habit, but rather to a lessening
thereof.

From this it is clear how to solve the objections.
_________________