[Footnote 2: Rise and Influence, of Rationalism in Europe, vol. ii. p. 261.]
[Footnote 3: Endemann, Studien, vol. i. p. 17.]
In answer to the question 'whether it is a sin to take usury for money lent,' Aquinas replies: 'To take usury for money lent is unjust in itself, because this is to sell what does not exist, and this evidently leads to inequality, which is contrary to justice.
'In order to make this evident, we must observe that there are certain things the use of which consists in their consumption; thus we consume wine when we use it for drink, and we consume wheat when we use it for food. Wherefore in such-like things the use of the thing must not be reckoned apart from the thing itself, and whoever is granted the use of the thing is granted the thing itself; and for this reason to lend things of this kind is to transfer the ownership. Accordingly, if a man wanted to sell wine separately from the use of the wine, he would be selling the same thing twice, or he would be selling what does not exist, wherefore he would evidently commit a sin of injustice. In like manner he commits an injustice who lends wine or wheat, and asks for double payment, viz. one, the return of the thing in equal measure, the other, the price of the use, which is called usury.
'On the other hand, there are other things the use of which does not consist in their consumption; thus to use a house is to dwell in it, not to destroy it. Wherefore in such things both may be granted; for instance, one man may hand over to another the ownership of his house, while reserving to himself the use of it for a time, or, vice versa, he may grant the use of a house while retaining the ownership. For this reason a man may lawfully make a charge for the use of his house, and, besides this, revendicate the house from the person to whom he has granted its use, as happens in renting and letting a house.
'But money, according to the philosopher,[1] was invented chiefly for the purpose of exchange; and consequently the proper and principal use of money is its consumption or alienation, whereby it is sunk in exchange. Hence it is by its very nature unlawful to take payment for the use of money lent, which payment is known as usury; and, just as a man is bound to restore other ill-gotten goods, so he is bound to restore the money which he has taken in usury.'[2]
[Footnote 1: Eth. v. Pol. 1.]
[Footnote 2: II. ii. 78, 1.]
The essential thing to notice in this explanation is that the contract of mutuum is shown to be a sale. The distinction between things which are consumed in use (res fungibiles), and which are not consumed in use (res non fungibiles) was familiar to the civil lawyers; but what they had never perceived was precisely what Aquinas perceived, namely, that the loan of a fungible thing was in fact not a loan at all, but a sale, for the simple reason that the ownership in the thing passed. Once the transaction had been shown to be a sale, the principle of justice to be applied to it became obvious. As we have seen above, in treating of sales, the essential basis of justice in exchange was the observance of aequalitas between buyer and seller—in other words, the fixing of a just price. The contract of mutuum, however, was nothing else than a sale of fungibles, and therefore the just price in such a contract was the return of fungibles of the same value as those lent. If the particular fungible sold happened to be money, the estimation of the just price was a simple matter—it was the return of an amount of money of equal value. As money happened to be the universal measure of value, this simply meant the return of the same amount of money. Those who maintained that something additional might be claimed for the use of the money lost sight of the fact that the money was incapable of being used apart from its being consumed.[1] To ask for payment for the sale of a thing which not only did not exist, but which was quite incapable of existence, was clearly to ask for something for nothing—which obviously offended against the first principles of commutative justice. 'He that is not bound to lend,' says Aquinas in another part of the same article, 'may accept repayment for what he has done, but he must not exact more. Now he is repaid according to equality of justice if he is repaid as much as he lent, wherefore, if he exacts more for the usufruct of a thing which has no other use but the consumption of its substance, he exacts a price of something non-existent, and so his exaction is unjust.'[2] And in the next article the principle that mutuum is a sale appears equally clearly: 'Money cannot be sold for a greater sum than the amount lent, which has to be paid back.'[3]
[Footnote 1: Aquinas did not lose sight of the fact that money might, in certain cases, be used apart from being consumed—for instance, when it was not used as a means of exchange, but as an ornament. He gives the example of money being sewn up and sealed in a bag to prevent its being spent, and in this condition lent for any purpose. In this case, of course, the transaction would not be a mutuum, but a locatio et conductio, and therefore a price could be charged for the use of the money (Quaestiones Disputatae de Malo, Q. xiii. art. iv. ad. 15, quoted in Cronin's Ethics, vol. ii. p. 332).]