l to induce a man to sin, yet it is
lawful to make use of another's sin for a good end, since even God
uses all sin for some good, since He draws some good from every
evil.... Accordingly it is by no means lawful to induce a man to lend
under a condition of usury; yet it is lawful to borrow for usury from
a man who is ready to do so, and is a usurer by profession, provided
that the borrower have a good end in view, such as the relief of his
own or another's need.... He who borrows for usury does not consent
to the usurer's sin, but makes use of it. Nor is it the usurer's
acceptance of usury that pleases him, but his lending, which is
good.'[1]

[Footnote 1: II. ii. 78, 4.]

We should mention here the _montes pietatis_, which occupied a
prominent place among the credit-giving agencies of the later Middle
Ages, although it is difficult to say whether their methods were
examples of or exceptions to the doctrines forbidding usury. These
institutions were formed on the model of the _montes profani_, the
system of public debt resorted to by many Italian States. Starting in
the middle of the twelfth century,[1] the Italian States had
recourse to forced loans in order to raise reserves for extraordinary
necessities, and, in order to prevent the growth of disaffection among
the citizens, an annual percentage on such loans was paid. A fund
raised by such means was generally called a _mons_ or heap. The
propriety of the payment of this percentage was warmly contested
during the fourteenth and fifteenth centuries--the Dominicans and
Franciscans defending it, and the Augustinians attacking it. But its
justification was not difficult. In the first place, the loans were
generally, if not universally, forced, and therefore the payment of
interest on them was purely voluntary. As we have seen, Aquinas was
quite clear as to the lawfulness of such a voluntary payment. In
the second place, the lenders were almost invariably members of
the trading community, who were the very people in whose favour a
recompense for _lucrum cessans_ would be allowed.[2] Laurentius de
Rodulphis argued in favour of the justice of these State loans, and
contended that the bondholders were entitled to sell their rights, but
advised good Christians to abstain from the practice of a right about
the justice of which theologians were in such disagreement[3]; and
Antoninus of Florence, who was in general so strict on the subject of
usury, took the same view.[4]