Money, explained · the reference layer

Interest and usury

Updated 2026-07-31 · Sources: 9 · 18 entries

For most of Christian history, charging interest on a loan was a sin with a name. Then it became a product with a rate. This page is the story of how that happened, told without pretending the argument is over.

The one thing to remember: the word usury has changed meaning underneath us. For Aquinas it meant any charge for the use of a loan. For a modern reader it means an unfairly high one. Half the confusion in Christian conversation about debt comes from those two meanings sharing a word.

First, the covenant setting

Israel's interest laws are civil legislation for a covenant nation, in an agrarian economy where land was allotted by tribe, sold back at Jubilee, and where a loan almost always meant a neighbour in trouble. There was no consumer credit market, no business lending market, and no mortgage. When Exodus says not to be as a moneylender to a poor brother, it is regulating relief to a distressed member of the same covenant family, not pricing capital.

That context does not weaken the commands; it aims them. Read as economic policy for a modern state, they are being read out of position. Read as what they are (God legislating that the covenant community will not turn its own members' emergencies into a revenue stream), they land hard, and they land on us. This is the standing rule on this site for Old Testament civil law; see how we read Scripture.

Deuteronomy 23:19-20 adds the clause that has generated two millennia of argument: no interest to a brother, but interest may be taken from a foreigner. Whatever else it means, it means the prohibition was not a claim that interest is intrinsically evil in every relationship. The prophets and the Psalms then treat exacting interest from the poor as a mark of the unrighteous (Psalm 15:5; Ezekiel 18:8), and Nehemiah 5 records a governor forcing the nobles to give it back (the one place in Scripture where a debt crisis is resolved on the page).

The long timeline

Aristotle’s argument, and why it mattered so much

In the first book of the Politics, Aristotle distinguishes household management from the art of making money, and puts lending at interest at the bottom of the second category: money was invented for exchange, and to make money breed money is to use it against its nature. He was writing three centuries before Christ, for a Greek audience, with no reference to Israel's law. But the argument was philosophically portable, and when medieval theologians rediscovered Aristotle they found a rational case that matched the scriptural one. That fusion is what made the prohibition so durable: it was not merely commanded, it was thought to be demonstrable.

Aquinas gives it its sharpest form. Some things are consumed in their use: wine, bread, money. For those, ownership and use cannot be sold separately, because using them is spending them. To lend a sum and charge both for its return and for its use is to sell the same thing twice. Whatever you think of the conclusion, notice that it is an argument about the nature of the thing, not a proof text. That is why the exceptions, when they came, had to be arguments too.

The exceptions that ate the rule

Medieval canonists were not naive about commerce, and they built a set of legitimate titles to a return. If lending cost the lender an actual loss, he could be compensated (damnum emergens). If it cost him a profit he would otherwise have made, that too was arguable (lucrum cessans). A penalty could be attached to late repayment. Beyond that, partnerships shared risk and therefore shared profit legitimately; a census was a purchase of a future income stream rather than a loan; and by the fifteenth century the "triple contract" combined a partnership with two insurance contracts to yield something that behaved exactly like a fixed-interest loan while remaining formally licit.

Meanwhile the church founded lending institutions of its own. The montes pietatis, charitable pawn banks for the poor, were approved by the Fifth Lateran Council in 1515, with a modest charge, defended as covering costs rather than as interest. The distinction between a fee and a rate has been doing heavy lifting for a very long time.

The Reformation hinge

Luther, in 1524, held the traditional line and had little patience for the evasions, though he accepted that the civil magistrate had to govern an economy that would not obey the ideal. Calvin made the move that changed the conversation. In a letter written in 1545 to his correspondent Claude de Sachin (a private reply rather than a published treatise, which is part of why its permission travels more widely than its conditions), he argued that Scripture's prohibition targets loans to the needy, that the Deuteronomy exception shows the ban is not a universal natural law, and that money lent to a merchant who will profit by it is not the same act as money lent to a starving neighbour. He then attached conditions that are rarely quoted alongside the permission: never take interest from the poor, never exceed what the law allows, never let lending become one's trade, and always ask whether the borrower gains at least as much as the lender. He made substantially the same case in print in his commentary on Ezekiel 18, which is the Calvin source listed at the foot of this page; the 1545 letter itself survives in the collected correspondence rather than in that volume, and is worth reading whole before anyone cites him as the man who approved of interest.

English law moved with the same current: interest legalised up to ten percent in 1545, repealed in 1552, restored in 1571. Note what happens to the vocabulary. Once a legal ceiling exists, "usury" stops meaning interest and starts meaning interest above the ceiling. The Catholic position followed a slower version of the same path: Vix Pervenit in 1745 restated the principle while conceding the extrinsic titles, and by the 1917 Code of Canon Law church bodies could take the legal rate.

The modern shape of the problem

Britain repealed its usury statutes in 1854. The United States kept state rate ceilings until a 1978 Supreme Court decision let a national bank export its home state's rate to borrowers everywhere; South Dakota removed its cap in 1980, card issuers moved, and the ceilings stopped binding. What remains are targeted caps rather than general ones, most visibly the Military Lending Act of 2006, which caps most consumer credit to servicemembers at a 36 percent military annual percentage rate.

The result is a credit market with an enormous spread. A well-secured mortgage may cost a few percent. A credit card carried month to month typically costs somewhere in the high teens or twenties; the Federal Reserve publishes the average in its G.19 release. A payday loan, priced as a flat fee on a two-week advance, commonly works out at an annual rate in the hundreds of percent, and the Consumer Financial Protection Bureau's own materials show how that arithmetic runs. The medieval question is still live; it has simply moved from whether interest is licit to who pays the highest rate and why.

Where the debate stands

Islamic jurisprudence took the first road and stayed on it. The prohibition of riba is treated as binding, and modern Islamic finance is built around profit-sharing, leasing and cost-plus sale structures that reach commercial ends without a stated interest rate, structurally a close cousin of the scholastic workarounds, and subject to the same criticism that form may be doing the work that substance should.

On the lender's side the New Testament is not silent. Jesus tells disciples to lend without expecting anything back: a command about generosity toward those who cannot repay, which cuts against the whole logic of pricing risk, and which no rate ceiling satisfies.

Go deeper

• Question: Is debt a sin?: the borrower’s side of this page, answered short.
• Question: Are credit cards wrong for Christians?: the modern rate the usury argument now runs into.
• Question: Should I cosign a loan or lend to family?: lending inside the family, now.
• Theme: debt, borrowing, surety: including whether Romans 13:8 forbids borrowing.
• How we read Scripture on money: the covenant-context rule this page runs on.
• Lesson: interest, the price of time.
• Lesson: predatory products: where the modern usury question actually bites.
• Tool: Debt Spiral: minimum payments, drawn out.
• How banks create money: what the lender is actually lending.