3. Private exchange begins in the need of at least one of the contracting parties. It is an act of charity in the other party to accommodate him by offering the thing needed. If the offer is made otherwise than as a gift, and is accepted, he who avails himself of it is bound in justice to see that the afforder of the accommodation is compensated for the loss that he suffers in affording it. Thus far the recipient is bound in justice, and no further in that virtue. However wholesome or profitable the thing be to him that gets it, the supplier cannot charge for that but only for the loss that he himself suffers, or the gain that he foregoes, in handing the thing over, or the pains that he takes, or the hardship that he endures, or the risk that he runs, in rendering the service desired. If all the labour to be undergone, or damage incurred, or risk encountered, by the sailor who goes about by private bargain to be my ferryman, is fairly met by the remuneration of a thirty-shilling watch, he has no right to stipulate for any more, not though the passage that he gives me sets me on the way to a throne. The peculiar advantage that I have in prospect does not come out of him, but out of myself. He must not pretend to sell what is not his, what attaches, not to him, but to me. He can only sell his own loss, risk, pains and labour. At the same time, if I have any gentlemanly or generous feeling in me, I shall be forward to bestow extra remuneration on one who has rendered me so timely a service: but this is matter of my gratitude, not of his right and claim in justice. Gratitude must not be put into the bill. And this much of private exchange.
4. Commercial exchange is conducted according to market value. Apart from dire necessity—and one in dire necessity is not fit to enter into commercial exchanges—the rule is, that a seller may always ask the market value of his article, however much that may be above what the thing cost him, or the use value which it bears to him. Thus, if one finds in his garden a rare Roman coin—so far as his tastes go, a paltry bit of metal—he may sell it for whatever price numismatists will offer: whereas, if there were no market for coins, but only one individual who doted on such things, the finder could make no profit out of that individual, the coin having neither market value with the community, nor use value in the eyes of the finder.
5. As there is a twofold value, and a twofold exchange, so a twofold character is impressed on the great instrument of exchange, money. Money, in one character, is an instrument of private exchange: in its other character, to mercantile men more familiar, it is an instrument of commercial exchange. In the one, it represents use value to the particular owner, more or less to him than it would be to some other owner: in the other, it represents market value, the same to all at the same time.
6. Leo X. in the Fifth Council of Lateran, 1515, ruled that—"usury is properly interpreted to be the attempt to draw profit and increment, without labour, without cost, and without risk, out of the use of a thing that does not fructify." In 1745 Benedict XIV. wrote in the same sense to the Bishops of Italy: "That kind of sin which is called usury, and which has its proper seat and place in the contract of mutuum, consists in turning that contract, which of its own nature requires the amount returned exactly to balance the amount received, into a ground for demanding a return in excess of the amount received." Mutuum, be it observed, is a loan for a definite period, of some article, the use of which lies in its consumption, as matches, fuel, food, and, in one respect, money. We shall prove this to be properly a gratuitous contract. (s. iv., n. 4, p. 254.)
7. Usury then is no mere taking of exorbitant interest. There is no question of more or less, but it is usury to take any interest at all upon the loan of a piece of property, which
(a) is of no use except to be used up, spent, consumed:
(b) is not wanted for the lender's own consumption within the period of the loan:
(c) is lent upon security that obviates risk:
(d) is so lent that the lender foregoes no occasion of lawful gain by lending it.
8. When all these four conditions are fulfilled, and yet interest is exacted upon a loan, such interest is usurious and unjust. And why? Simply by reason of the principle that we laid down before, speaking of private exchange (n. 3), a principle that is thus stated by St. Thomas: