HTH ARTICLE [II-II, Q. 158, Art. 8]

Whether There Is a Vice Opposed to Anger Resulting from Lack of Anger?

Objection 1: It would seem that there is not a vice opposed to anger,
resulting from lack of anger. For no vice makes us like to God. Now
by being entirely without anger, a man becomes like to God, Who
judges "with tranquillity" (Wis. 12:18). Therefore seemingly it is
not a vice to be altogether without anger.

Obj. 2: Further, it is not a vice to lack what is altogether useless.
But the movement of anger is useful for no purpose, as Seneca proves
in the book he wrote on anger (De Ira i, 9, seqq.). Therefore it
seems that lack of anger is not a vice.

Obj. 3: Further, according to Dionysius (Div. Nom. iv), "man's evil
is to be without reason." Now the judgment of reason remains
unimpaired, if all movement of anger be done away. Therefore no lack
of anger amounts to a vice.

_On the contrary,_ Chrysostom [*Hom. xi in Matth. in the Opus
Imperfectum, falsely ascribed to St. John Chrysostom] says: "He who
is not angry, whereas he has cause to be, sins. For unreasonable
patience is the hotbed of many vices, it fosters negligence, and
incites not only the wicked but even the good to do wrong."

_I answer that,_ Anger may be understood in two ways. In one way, as
a simple movement of the will, whereby one inflicts punishment, not
through passion, but in virtue of a judgment of the reason: and thus
without doubt lack of anger is a sin. This is the sense in which
anger is taken in the saying of Chrysostom, for he says (Hom. xi in
Matth., in the Opus Imperfectum, falsely ascribed to St. John
Chrysostom): "Anger, when it has a cause, is not anger but judgment.
For anger, properly speaking, denotes a movement of passion": and
when a man is angry with reason, his anger is no longer from passion:
wherefore he is said to judge, not to be angry. In another way anger
is taken for a movement of the sensitive appetite, which is with
passion resulting from a bodily transmutation. This movement is a
necessary sequel, in man, to the movement of his will, since the
lower appetite necessarily follows the movement of the higher
appetite, unless there be an obstacle. Hence the movement of anger in
the sensitive appetite cannot be lacking altogether, unless the
movement of the will be altogether lacking or weak. Consequently lack
of the passion of anger is also a vice, even as the lack of movement
in the will directed to punishment