What is money?

Credit is a memory with a number attached.

Bob gives Alice the shoes now. In return, he receives a claim on something Alice will provide later. They have created a debt: a promise about a future transfer, expressed with enough confidence to be written down.

Write many such promises in a common unit and you have a ledger. Allow the claims to pass between people and the promises begin to behave like money. Participants no longer need to remember the original favor. They need only remember the amount, which can be made considerably larger.

Money is accepted individually because it has already been accepted collectively.

This may sound like belief, but belief is not strictly necessary. A shopkeeper can dislike the currency, distrust the banking system, and remain deeply concerned about inflation while still accepting payment. Coordination asks less than confidence. It requires only that everyone behave as though everyone else will continue behaving similarly until closing time.

Each successful payment provides evidence that the next payment will also succeed. Yesterday supports today, today supports tomorrow, and tomorrow will support the following day once it has occurred. The system does not depend on universal agreement. It depends on disagreement being conducted in the agreed currency.

Interest is the price of moving money through time.

Suppose Alice lends Bob $100 for one year at five percent. Alice gives up a present $100 and receives a future $105. The additional five dollars compensate her for spending one year with the wrong amount of money. Bob receives the useful part first and pays for the distance afterward.

Viewed from the future, $105 becomes $100 when discounted back to today. The same five dollars are added when the calculation moves forward and removed when it moves backward, demonstrating that time has a preferred financial direction. Longer periods usually require more interest because the money must pass through more future before returning.

Banking turns one person’s future payment into another person’s present balance.

The bank’s loan is supported by the borrower’s income and collateral. The bank’s deposit is supported by its loans, reserves, capital, and access to other banks. Those banks are supported by their own loans, reserves, capital, and access to the first bank. Each obligation therefore rests on a lower layer of obligations, except where the diagram ends.

Not every promise must be fulfilled at the same moment. Depositors withdraw at different times, borrowers repay over many years, and assets are sold when a suitable buyer has also decided not to wait. This allows stability to be constructed from debts arranged in sufficiently reassuring layers, provided the layers are inspected one at a time.

Demand is money pointing at something.

When more money points at the same quantity of an object, the price usually rises. The higher price causes some of the money to point elsewhere, restoring balance. Supply works in the opposite direction by producing additional objects for the money to point at.

Inflation occurs when this happens to many objects at approximately the same time. Because it would be impractical to ask every object, statisticians maintain a representative basket. The items are placed in the basket conceptually; the basket itself is excluded because pricing it would alter the result.

A payment is a coordinated disagreement.

Suppose Alice pays Bob $20. Alice’s bank subtracts $20 and Bob’s bank adds $20. For a short period, the banks hold different accounts of what has occurred. Settlement resolves the disagreement by moving reserves until both versions of the money are true.

If Bob pays Carol the same $20, total spending is now $40 even though only $20 has participated. Economists call this velocity. The money has not multiplied; it has simply been counted at each place where it was recently relevant.

A forecast is the future adjusted for what can be entered into a cell.

Economists combine employment, prices, spending, interest rates, rainfall, and several measures of confidence in a model. The model then produces a central path surrounded by less central paths. Events near the central path were expected. Events farther away are described as uncertainty until they occur, at which point they become data.

The forecast is also part of the system it forecasts. If it predicts a recession, banks may lend less, firms may delay investment, and households may begin behaving like households in a recession. If the recession follows, the model identified it. If it does not, the warning may have prevented it. Both results justify another forecast.

A financial crisis is the sudden requirement that promises become specific.

Governments and central banks respond with guarantees, emergency loans, asset purchases, and carefully chosen nouns. An uncertain private promise is replaced by a more convincing public promise, usually before the public has been told exactly what it is promising. This restores confidence by moving the question to an institution large enough to answer it later.

The loss itself does not disappear. It can be assigned to shareholders, creditors, deposit insurers, taxpayers, future taxpayers, currency holders, or a footnote describing extraordinary measures. Once the number has been divided among enough balance sheets, no single institution contains the entire emergency and the process is called resolution.

The definition is complete.

Money has value because it can be exchanged for valuable things. Valuable things are those for which people exchange money. This relationship is circular, but circles are among the most stable shapes and are therefore widely used in economics.

The earlier cases now fit together. Credit is money remembered before it is paid. Reserves are money used by institutions that issue other money. Prices are money expressed as objects, and spending is money becoming someone else’s money. Nothing remains unexplained except why this explanation is sufficient.