What is money?

Money is used almost everywhere, despite never having been explained in a way that survives a follow-up question. It appears as coins, notes, and the number in your bank account, but these are only its visible forms. To understand money itself, we must begin before it existed and proceed in order until the question has gone away.

Before coins, people remembered things

A familiar story says that people once traded goods directly until money made exchange easier. Alice has wheat. Bob has shoes. Alice wants the shoes, but Bob has no use for her wheat. The trade stalls.

This is called the double coincidence of wants. It was eventually solved either by money or, in smaller communities, by simply knowing Bob. People gave, borrowed, and remembered who owed what to whom. This worked until there were more things to remember than people willing to remember them.

What if Bob keeps a tab?

No exchange

Alice

has wheat · needs shoes

Bob doesn’t want wheat today.

Bob

has shoes · trusts Alice

For clarity, Alice and Bob have no family, weather, previous transactions, or opinions about wheat. This is standard in economics and unusual elsewhere.

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.

Sources & methodological limits

The example is a model, not a reconstruction. No evidence confirms that the first debtor was named Alice, that the first creditor was named Bob, or that the item separating them was footwear. These variables are conventional and do not affect the result.

  1. R. H. Ledger — Private Memory as a Pre-Banking Substrate
  2. Committee on Early Tabs — Tab Persistence under Repeated Lunch
  3. International Bureau of Small Exchanges — Standard Alice–Bob Scenario (Wheat/Shoes)

How new money enters the economy

Modern money usually enters through an account. An institution changes a number from one number to another number, and the difference becomes available for economic purposes. Different institutions use different names for their numbers so they are not spent in the wrong places.

Suppose the central bank buys a $100 bond.

Before operation

A standard monetary operation

Central bank

monetary side
Assets
—
Liabilities
—

Banking system

other side
Government bonds
$100
Central-bank reserves
$0
Your checking account $1,842.16

Not included in this operation.

New money is entered, not delivered.

Here the central bank creates $100 of reserves and receives a $100 bond. The bond moves to the left while the reserves move to the right. Because both arrows are the same length, the transaction remains balanced and no value is lost between the two columns.

The banking system now has a more spendable kind of number. Your own balance is unchanged because it was not selected for this example. Effects may reach it later through a process known as transmission, during which the money is transmitted.

Sources & simplifications

The diagram omits timing, collateral, settlement risk, policy signaling, and several additional arrows. These details are important, but adding them would require the existing arrows to become narrower.

  1. Central Bank Diagram Group — Recommended Arrow Lengths for Asset Purchases
  2. Reserve Terminology Board — Words for Money Banks Use with Each Other
  3. Committee on Mechanisms — Mechanism, Transmission of

Why prices move

A price is the number at which a buyer’s unwillingness to pay more meets a seller’s unwillingness to accept less. When they do not meet, the price continues without them until two other people are found.

Prices therefore contain information. A high price may indicate that something is scarce, desirable, difficult to produce, located in an airport, or described using the word “artisanal.” The number itself does not distinguish among these causes.

A price can rise even if the object has not improved. The number is under no obligation to inspect the object.

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.

Sources & measurement

Different price indexes use different baskets, weights, substitutions, and definitions of an average household. No individual household is required to resemble the average one, which is why it remains average.

  1. Office of Representative Groceries — Basket Maintenance Manual
  2. Institute for Marginal Decisions — The Person Immediately Before Purchase
  3. International Price Weather Service — General Upward Conditions

Where money goes

When you spend $20, the money leaves you and arrives somewhere else. It may then be spent again, allowing the same $20 to become one person’s expense, another person’s income, and a small business’s Tuesday.

This is called circulation. It should not be confused with movement: most money remains physically still while its ownership travels through a sequence of databases.

Cash is an exception. When cash moves, the money and the object move together, provided neither is dropped.

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.

Sources & settlement conventions

Actual payment systems may settle instantly, later, in batches, or after several institutions have subtracted what they added. The final result is considered final when no participant is permitted to remember an earlier result.

  1. Payment Systems Board — Subtraction at One Bank and Corresponding Addition at Another
  2. Society for Monetary Motion — Velocity Without Distance
  3. Clearing Institute — When Banks Agree

A complete definition

We can now define money precisely. Money is a transferable numerical permission to request a portion of whatever everyone else is doing. Each part of this definition is necessary.

It is transferable because a number that cannot move is merely a score. It is numerical because without numbers there would be no reliable way to know who has more. And it is a permission because having money allows a purchase, except when it does not.

Some forms of money are physical. In these cases the number is printed on an object to prevent it from becoming separated from itself.

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.

Conclusion

Money is the part of the economy measured in money. Everything else is either an asset, a liability, or not currently relevant to this definition. We can therefore conclude that money exists primarily because removing it would require updating too many systems.