"Usury", as found in "Essays of a Catholic"
by Hilaire Belloc
Suppose there is an oasis of date-palms in the desert, the water-supply of which is got at by very primitive means. There comes a financier who lends money for development. The capital is productively used; artesian wells are sunk; the water-supply is largely increased; a better organization of the date-cultivation is begun; the produce of the oasis rapidly grows from year to year; the profits legitimately demanded by the financier are a apart of the total extra annual wealth, the presence of which has been due to his enterprise. All are well-to-do; everything flourishes.
Then, whether through fatigue, or through war or pestilence, or variations in the eternal market, or some calamity of climate, things begin to go wrong. The annual wealth produced by the oasis declines. But the interest on the money lent must still be paid. As the cultivators get more and more embarrassed they borrow in order to pay that interest, and there comes a time of "overlap," during which, paradoxically enough, the banker appears to be more and more prosperous, though the community which supplies him is getting less and less so. But it is mere arithmetic that the process must come to an end. There will arrive a moment after which the cultivator can no longer find the money to pay the interest, which has long since ceased to be morally due. Mere coercion under an all-powerful police system has got the last penny out of him. The "overlap" between real prosperity and apparent-merely financial or paper- prosperity ceases; and the temporary wealth enjoyed by the lender comes to an end, as had previously come to an end the real prosperity of the borrower.
In other words, great banking prosperity in any particular period may be, and commonly is, the proof of all-round prosperity in that period; but it is not necessarily nor always so. The one is not an inevitable adjunct of the other.