in his turn the former has conferred on him. Therefore he that
first conferred a favor will be bound to a yet greater repayment, and
so on indefinitely. Now virtue does not strive at the indefinite,
since "the indefinite removes the nature of good" (Metaph. ii, text.
8). Therefore repayment of gratitude should not surpass the favor
received.

Obj. 3: Further, justice consists in equality. But "more" is excess
of equality. Since therefore excess is sinful in every virtue, it
seems that to repay more than the favor received is sinful and
opposed to justice.

_On the contrary,_ The Philosopher says (Ethic. v, 5): "We should
repay those who are gracious to us, by being gracious to them
return," and this is done by repaying more than we have received.
Therefore gratitude should incline to do something greater.

_I answer that,_ As stated above (A. 5), gratitude regards the favor
received according the intention of the benefactor; who seems be
deserving of praise, chiefly for having conferred the favor gratis
without being bound to do so. Wherefore the beneficiary is under a
moral obligation to bestow something gratis in return. Now he does
not seem to bestow something gratis, unless he exceeds the quantity
of the favor received: because so long as he repays less or an
equivalent, he would seem to do nothing gratis, but only to return
what he has received. Therefore gratitude always inclines, as far as
possible, to pay back something more.

Reply Obj. 1: As stated above (A. 3, ad 5; A. 5), in repaying favors
we must consider the disposition rather than the deed. Accordingly,
if we consider the effect of beneficence, which a son receives from
his parents namely, to be and to live, the son cannot make an equal
repayment, as the Philosopher states (Ethic. viii, 14). But if we
consider the will of the giver and of the repayer, then it is
possible for the son to pay back something greater to his father, as
Seneca declares (De Benef. iii). If, however, he were unable to do
so, the will to pay back would be sufficient for gratitude.

Reply Obj. 2: The debt of gratitude flows from charity, which the
more it is paid the more it is due, according to Rom. 13:8, "Owe no
man anything, but to love one another." Wherefore it is not
unreasonable if the obligation of gratitude has no limit.

Reply Obj. 3: As in injustice, which is a cardinal virtue, we
consider equality of things, so in gratitude we consider equality of
wills. For whi