, for this is not to sell the use of money but to avoid
a loss. It may also happen that the borrower avoids a greater loss
than the lender incurs, wherefore the borrower may repay the lender
with what he has gained. But the lender cannot enter an agreement for
compensation, through the fact that he makes no profit out of his
money: because he must not sell that which he has not yet and may be
prevented in many ways from having.

Reply Obj. 2: Repayment for a favor may be made in two ways. In one
way, as a debt of justice; and to such a debt a man may be bound by a
fixed contract; and its amount is measured according to the favor
received. Wherefore the borrower of money or any such thing the use
of which is its consumption is not bound to repay more than he
received in loan: and consequently it is against justice if he be
obliged to pay back more. In another way a man's obligation to
repayment for favor received is based on a debt of friendship, and
the nature of this debt depends more on the feeling with which the
favor was conferred than on the greatness of the favor itself. This
debt does not carry with it a civil obligation, involving a kind of
necessity that would exclude the spontaneous nature of such a
repayment.

Reply Obj. 3: If a man were, in return for money lent, as though
there had been an agreement tacit or expressed, to expect or exact
repayment in the shape of some remuneration of service or words, it
would be the same as if he expected or exacted some real
remuneration, because both can be priced at a money value, as may be
seen in the case of those who offer for hire the labor which they
exercise by work or by tongue. If on the other hand the remuneration
by service or words be given not as an obligation, but as a favor,
which is not to be appreciated at a money value, it is lawful to
take, exact, and expect it.

Reply Obj. 4: Money cannot be sold for a greater sum than the amount
lent, which has to be paid back: nor should the loan be made with a
demand or expectation of aught else but of a feeling of benevolence
which cannot be priced at a pecuniary value, and which can be the
basis of a spontaneous loan. Now the obligation to lend in return at
some future time is repugnant to such a feeling, because again an
obligation of this kind has its pecuniary value. Consequently it is
lawful for the lender to borrow something else at the same time, but
it is unlawful for him to bind the borrower to grant