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Thomas Aquinas is acclaimed as the father of Roman Catholic theology. A student of Aristotle’s philosophy, he applied logic and moral discernment to the complex realities of medieval life. Here we excerpt from his master work, Summa Theologica, parts of his treatises on “Cheating” and “The Sin of Usury.”

Whether, in Trading, It Is Lawful to Sell a Thing at a Higher Price Than What Was Paid for It?

THE GREEDY TRADESMAN blasphemes over his losses; he lies and perjures himself over the price of his wares. But these are vices of the man, not of the craft, which can be exercised without these vices. Therefore trading is not in itself unlawful.

I answer that. A tradesman is one whose business consists in the exchange of things. According to the Philosopher, exchange of things is twofold; one, natural as it were, and necessary, whereby one commodity is exchanged for another, or money taken in exchange for a commodity, in order to satisfy the needs of life. Suchlike trading, properly speaking, does not belong to the tradesmen, but rather to housekeepers or civil servants who have to provide the household or the state with the necessaries of life. The other kind of exchange is either that of money for money, or of any commodity for money, not on account of the necessities of life, but for profit, and this kind of exchange, properly speaking, regards tradesmen, according to the Philosopher. The former kind of exchange is commendable because it supplies a natural need: but the latter is justly deserving of blame, because, considered in itself, it satisfies the greed for gain, which knows no limit and tends to infinity. Hence trading, considered in itself, has a certain debasement attaching thereto, in so far as, by its very nature, it does not imply a virtuous or necessary end. Nevertheless gain which is the end of trading, though not implying, by its nature, anything virtuous or necessary, does not, in itself, connote anything sinful or contrary to virtue: wherefore nothing prevents gain from being directed to some necessary or even virtuous end, and thus trading becomes lawful. Thus, for instance, a man may intend the moderate gain which he seeks to acquire by trading for the upkeep of his household, or for the assistance of the needy: or again, a man may take to trade for some public advantage, for instance, lest his country lack the necessaries of life, and seek gain, not as an end, but as payment for his labour.

Whether It Is a Sin to Take Usury for Money Lent?

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 suchlike 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 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 the 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.

Now money, according to the Philosopher 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 is he bound to restore the money which he has taken in usury.

By Thomas Aquinas

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