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Money and credit theory is the branch of monetary economics that asks what money is, why it exists, and how credit—the promise to pay money later—relates to money itself. Its central questions are deceptively simple: What makes something money? Is money a thing, a claim, or a social relation? Does credit create money, or does money make credit possible? And what happens to the economy when the distinction between money and credit blurs, as it does in modern banking systems?
The subfield is not primarily about monetary policy—interest rates, inflation targeting, or central bank rules—though it supplies the conceptual foundations for those practical questions. Rather, it is about the nature of the monetary system itself: how money emerges, how it is measured, how banks create it, and how the promises that constitute credit can become the medium of exchange.
Any serious treatment of money and credit must confront a definitional puzzle. Money is commonly described by its functions: it is a medium of exchange, a unit of account, a store of value, and a standard of deferred payment. But functional definitions are incomplete. They describe what money does, not what money is. A cigarette in a prisoner-of-war camp serves as a medium of exchange, but it is not money in the same sense as a banknote. Conversely, the unit of account in which prices are quoted—say, the dollar—need not correspond to any physical object that circulates.
The deeper question is whether money is fundamentally a commodity, a claim, or a social convention. The commodity view holds that money emerged from barter as a particularly saleable good—gold, silver, salt—whose physical properties made it a natural medium of exchange. The claim view holds that money is always a form of credit: a token that represents a debt owed by its issuer. The social-convention view holds that money is whatever a community agrees to accept in settlement, whether or not it has intrinsic value or a backing promise.
These three views are not merely academic. They generate different accounts of how money began, how banks work, and what central banks actually do. They also shape how economists interpret the relationship between money and credit—whether the two are fundamentally distinct categories or two sides of the same ledger.
The commodity theory of money is the oldest and most intuitive account. In its classic form, it argues that money arose to solve the inefficiencies of barter. A baker who wants shoes must find a shoemaker who wants bread; money solves this "double coincidence of wants" by providing a universally acceptable good that can be exchanged for anything. Gold and silver were natural candidates because they were durable, divisible, portable, and scarce.
This account has deep roots. Aristotle described money as a convention that arose to facilitate exchange, and later classical economists—notably Adam Smith—popularized the barter-to-money story. In the nineteenth century, the commodity view became the foundation of the gold standard: if money is essentially a metal, then paper notes are merely convenient claims to that metal, and their value derives from convertibility.
The commodity theory has important strengths. It explains why certain goods historically served as money, and it captures an important truth: for most of recorded history, money was indeed a physical commodity, usually a precious metal. But it has serious limitations. Anthropological and historical research has found little evidence that pure barter economies ever existed as the universal precursor to money. Many societies used credit systems—recorded debts and obligations—long before they coined metal. The commodity theory also struggles to explain modern fiat money, which has no commodity backing and is money simply because the state declares it legal tender and accepts it for taxes.
The most influential modern defender of the commodity tradition was Carl Menger, whose 1892 article "On the Origin of Money" argued that money emerged spontaneously from the self-interested choices of traders who gradually recognized that certain goods were more saleable than others. Menger's account is more sophisticated than the simple barter story: it does not require a social contract or state decree, only the gradual convergence of individual behavior on a single medium. This "evolutionary" account remains influential, particularly among economists who see money as a market phenomenon rather than a state creation.
The credit theory of money inverts the commodity story. It holds that money is not a thing but a social relation—specifically, a claim on the issuer. In this view, the original form of money was not a coin but a debt: a tally, a clay tablet recording a loan, or a promise to deliver grain at harvest time. Money is not the object exchanged but the unit in which debts are denominated and settled.
This tradition has ancient roots. In Mesopotamia, thousands of years before coinage, temple and palace economies recorded debts and credits in barley and silver units. The Roman jurists distinguished between the physical coin and the money of account—the unit in which debts were expressed. But the credit theory found its most systematic modern expression in the late nineteenth and early twentieth centuries, in the work of writers such as Henry Dunning Macleod, Alfred Mitchell-Innes, and later the heterodox economist A. Mitchell Innes, whose 1913 and 1914 essays argued that "money is credit" and that even coinage was originally a token of debt.
The credit theory has a powerful modern application: the explanation of banking. When a bank makes a loan, it does not lend out existing deposits. It creates new money by crediting the borrower's account. The loan is an asset for the bank and a liability for the borrower; the deposit is a liability for the bank and an asset for the borrower. Both are entries on a ledger. This is why the credit view is sometimes called the "ledger" theory of money: money is not a stock of physical objects but a system of accounting entries.
The credit theory also explains the role of the state. If money is fundamentally a claim, then the question arises: a claim on whom? The answer, in the "chartalist" or "state theory of money" developed by the German economist Georg Friedrich Knapp in 1905, is that money is whatever the state accepts in payment of taxes. The state does not need to mint coins or print notes; it only needs to declare that certain tokens will be accepted at the treasury. This creates a demand for those tokens, and they become money. Knapp's term "chartal" (from the Latin charta, meaning ticket or token) emphasized that money is a token created by law, not a commodity with intrinsic value.
The credit and chartalist traditions have been revived in recent decades by "modern monetary theory" (MMT), which draws on Knapp, Mitchell-Innes, and the economist Hyman Minsky. MMT argues that a sovereign government that issues its own currency cannot run out of money, because it is the monopoly issuer of that currency. Taxes, in this view, do not fund government spending; they create demand for the currency and manage inflation. MMT remains controversial within the economics profession, but it has brought the credit theory of money back into mainstream debate.
The relationship between money and credit became a central policy controversy in nineteenth-century Britain, in the debates between the Currency School and the Banking School. These were not merely academic disputes; they shaped the structure of modern central banking.
The Currency School argued that banknotes should be treated as money and should be regulated like coin. Its members, including David Ricardo and later Robert Peel, believed that if banks could issue notes freely, they would overissue, causing inflation and financial instability. Their solution was the Currency Principle: notes should be issued only against gold reserves, so that the note supply would expand and contract exactly as a metallic currency would. This principle was enacted in the Bank Charter Act of 1844, which required the Bank of England to back its notes with gold beyond a fixed fiduciary issue.
The Banking School, led by Thomas Tooke and John Fullarton, argued that this analysis confused money with credit. Banknotes, they said, are not money but credit instruments—promises to pay money. And credit cannot be overissued, because it is created only in response to the needs of trade. If a bank makes too many loans, the borrowers will use the proceeds to repay debts or buy goods, and the notes will return to the bank for redemption. The Banking School's "law of reflux" held that credit is self-limiting: any excess will flow back to the issuer.
The Currency School won the legislative battle, but the Banking School won the intellectual war—at least in part. Modern central banks do not operate on the Currency Principle; they do not back their liabilities with gold, and they actively manage the money supply. But the quantity theory of money, which the Currency School championed, remains a central framework in monetary economics. The quantity theory holds that the price level is proportional to the money supply, other things equal. It is usually expressed through the equation of exchange, $MV = PY$, where M is the money supply, V is the velocity of money, P is the price level, and Y is real output. The quantity theory does not require that money be a commodity; it applies equally to fiat money. But it does require a clear distinction between money and credit, and it assumes that the money supply is something that can be measured and controlled.
The nineteenth-century debates also raised a question that remains unresolved: where does the boundary between money and credit lie? A banknote is money; a government bond is credit; but a bank deposit is both—a credit claim on the bank that functions as money. The modern answer is to define money by its liquidity: money is the set of assets that can be used directly for transactions, and credit is the set of promises that must be converted into money first. But this is a practical convention, not a theoretical solution.
The Austrian school of economics, founded by Carl Menger and developed by Eugen von Böhm-Bawerk and Ludwig von Mises, offers a distinctive theory of money and credit that ties them to the business cycle. The Austrian theory begins with Menger's account of money's spontaneous emergence, but it adds a crucial claim: money is not neutral. Changes in the money supply do not simply raise all prices proportionally; they alter relative prices and distort the structure of production.
The Austrian business cycle theory, most fully developed by Friedrich Hayek in the 1920s and 1930s, begins with the observation that banks can create credit money—deposits—without a corresponding increase in saving. When a bank lends newly created money, it drives the market interest rate below the "natural" rate that would equate saving and investment. This low interest rate signals to entrepreneurs that more long-term investment is profitable, and they undertake projects—factories, machinery, housing—that require time to complete.
But the new money does not create the real resources needed to complete these projects. When the money reaches workers and suppliers, they demand more consumption goods, and the prices of those goods rise. The interest rate eventually rises to reflect the true scarcity of capital, and the long-term projects become unprofitable. They are abandoned, and the economy enters a recession as resources are reallocated. The boom was an illusion created by credit expansion; the bust is the necessary correction.
The Austrian theory is not widely accepted in mainstream economics, which tends to explain recessions through sticky prices, demand shocks, or financial frictions. But it remains influential in certain policy circles, particularly among those who argue that central banks should not attempt to smooth the business cycle by expanding credit. The Austrian school also maintains a distinctive methodological stance: it rejects empirical testing in favor of logical deduction from axioms about human action. This makes it difficult to evaluate by conventional econometric methods, and its proponents see this as a strength rather than a weakness.
The post-Keynesian school, which draws on the work of John Maynard Keynes, Michał Kalecki, and Joan Robinson, offers a different account of money and credit, one that emphasizes the endogeneity of money. In the post-Keynesian view, the money supply is not determined by the central bank but by the demand for credit. Banks create money when they make loans, and the central bank accommodates the resulting demand for reserves. The causal chain runs from loans to deposits to reserves, not the reverse.
This "endogenous money" view has important implications. It means that the central bank cannot control the money supply directly; it can only set the interest rate at which it supplies reserves. It also means that the quantity theory of money is wrong, or at least misleading: the money supply is not an independent variable that determines the price level. Instead, prices are determined by costs—wages, materials, and profit margins—and money expands to finance those costs.
The post-Keynesian approach is closely associated with the "horizontalist" position of Nicholas Kaldor and Basil Moore, who argued that the money supply curve is horizontal at the central bank's chosen interest rate. Banks will supply any amount of credit demanded at that rate, as long as the borrower is creditworthy. The central bank's role is not to control the quantity of money but to set the price of reserves.
This view has been influential in the development of "modern monetary theory," which shares the post-Keynesian emphasis on endogenous money and the fiscal role of the state. But it also has critics within the post-Keynesian tradition itself. Some argue that the horizontalist position is too extreme: banks do not passively accommodate all demand for credit; they ration credit based on their assessment of borrower risk and their own capital constraints. This "structuralist" position, associated with Marc Lavoie and others, holds that the money supply is endogenous but not perfectly elastic.
A more recent development, sometimes called the "new monetary economics," questions the assumption that money must be a single thing that performs all functions simultaneously. This approach, associated with economists such as Robert Hall, Neil Wallace, and Eugene Fama, argues that the functions of money—medium of exchange, unit of account, store of value—can be separated and performed by different instruments.
In a fully developed financial system, the argument runs, there is no need for a special asset called money. Transactions can be settled by transferring claims on a diversified portfolio of assets, and prices can be quoted in a unit of account that is not itself a medium of exchange. Hall proposed a "nominal" unit of account defined by a basket of commodities, with payments made in whatever assets the parties agree to accept. Fama argued that banking could be organized as a pure "mutual fund" in which deposits are shares in a portfolio, not fixed-value claims.
This approach has not produced a practical reform proposal, but it has influenced the academic study of monetary economics by highlighting the contingency of money. It also provides a framework for thinking about cryptocurrencies and other digital assets, which separate the unit of account (the coin) from the medium of exchange (the blockchain) from the store of value (the underlying protocol). The new monetary economics is not a school in the sense of the Austrian or post-Keynesian traditions; it is more a research program that uses the separation of functions as an analytical device.
The contemporary study of money and credit theory is fragmented across several research traditions that coexist rather than succeed one another. Mainstream monetary economics, as taught in most graduate programs, is built on the "New Keynesian" synthesis, which combines microfoundations with sticky prices and treats money as a friction that can be modeled away. In this framework, the central bank sets interest rates, and the money supply adjusts endogenously; money itself plays little role in the analysis. This approach has been criticized for ignoring the very questions that define the subfield—what money is, how credit is created, and why the financial system is unstable.
Outside the mainstream, several heterodox traditions continue to develop. The post-Keynesian and MMT approaches emphasize the credit nature of money and the fiscal capacity of the state. The Austrian school maintains its critique of credit expansion and its commitment to methodological individualism. A growing "monetary theory" literature in economics and sociology draws on the work of Mitchell-Innes, Knapp, and Keynes to argue that money is fundamentally a social and political institution, not a market solution to barter.
The 2008 financial crisis and the subsequent European debt crisis brought these questions back to the center of public debate. The crisis was, at its core, a crisis of credit: banks had created vast quantities of money-like claims—asset-backed securities, repurchase agreements, money market fund shares—that were not money but could be used as if they were. When confidence collapsed, these claims could not be converted into money, and the financial system froze. This episode demonstrated that the boundary between money and credit is not fixed but is a matter of convention and regulation.
The rise of cryptocurrencies and central bank digital currencies has further unsettled the traditional categories. Bitcoin was designed as a commodity money for the digital age—a scarce, decentralized medium of exchange that requires no issuer. But it has functioned more as a speculative asset than as money, and its volatility makes it unsuitable as a unit of account. Central bank digital currencies, by contrast, would be state-issued digital money, potentially replacing bank deposits as the primary form of money. These developments have revived interest in the oldest questions of the subfield: What makes something money? Who should create it? And what is the relationship between the state, the banking system, and the medium of exchange?
The field of money and credit theory thus remains unsettled, not because its practitioners are ignorant but because its subject matter is inherently contested. Money is both a fact and a convention, both a thing and a relation, both a product of the market and a creation of the state. The different schools of thought are not simply competing explanations of the same phenomenon; they are different ways of seeing what the phenomenon is. A commodity theorist sees a gold coin; a credit theorist sees a ledger entry; a chartalist sees a tax receipt. The task of the subfield is not to decide which vision is correct but to understand how these different aspects of money interact—and what happens when they come apart.