it can ascend, but cannot
descend, i.e. decrease.

_I answer that,_ The quantity which charity has in comparison with
its proper object, cannot decrease, even as neither can it increase,
as stated above (A. 4, ad 2).

Since, however, it increases in that quantity which it has in
comparison with its subject, here is the place to consider whether it
can decrease in this way. Now, if it decrease, this must needs be
either through an act, or by the mere cessation from act. It is true
that virtues acquired through acts decrease and sometimes cease
altogether through cessation from act, as stated above (I-II, Q. 53,
A. 3). Wherefore the Philosopher says, in reference to friendship
(Ethic. viii, 5) "that want of intercourse," i.e. the neglect to call
upon or speak with one's friends, "has destroyed many a friendship."
Now this is because the safe-keeping of a thing depends on its cause,
and the cause of human virtue is a human act, so that when human acts
cease, the virtue acquired thereby decreases and at last ceases
altogether. Yet this does not occur to charity, because it is not the
result of human acts, but is caused by God alone, as stated above (A.
2). Hence it follows that even when its act ceases, it does not for
this reason decrease, or cease altogether, unless the cessation
involves a sin.

The consequence is that a decrease of charity cannot be caused except
either by God or by some sinful act. Now no defect is caused in us by
God, except by way of punishment, in so far as He withdraws His grace
in punishment of sin. Hence He does not diminish charity except by
way of punishment: and this punishment is due on account of sin.

It follows, therefore, that if charity decrease, the cause of this
decrease must be sin either effectively or by way of merit. But
mortal sin does not diminish charity, in either of these ways, but
destroys it entirely, both effectively, because every mortal sin is
contrary to charity, as we shall state further on (A. 12), and by way
of merit, since when, by sinning mortally, a man acts against
charity, he deserves that God should withdraw charity from him.

In like manner, neither can venial sin diminish charity either
effectively or by way of merit. Not effectively, because it does not
touch charity, since charity is about the last end, whereas venial
sin is a disorder about things directed to the end: and a man's love
for the end is none the less through his committing an inordinate