What is money? The problem Bitcoin was built to solve

Ask what is money and most people reach for the obvious: the notes folded in a wallet, the balance glowing in a banking app, the figure at the foot of a payslip. All correct, and none of it explains why an inert slip of paper and cotton commands an hour of skilled labour or a week's groceries. Seven years of explaining crypto to first-time readers taught me one lesson above all: you cannot really understand Bitcoin until you understand the thing it was built to fix. So before a single block or key, this guide answers a deceptively simple question, what is money, where did it come from, and why does almost every version of it eventually break?

What is money, really?

Money is any tool widely accepted for storing and moving value. Economists pin it down by three jobs it has to do: serve as a medium of exchange you can swap for goods and services, a store of value that keeps its worth between earning and spending, and a unit of account that lets you price wildly different things on a single scale.

Hold a $100 note up to the light and its uselessness is obvious. It is a thin slip of paper and cotton bearing a portrait of Benjamin Franklin, a serial number, and the claim that it is legal tender for all debts. You cannot eat it, wear it, or heat a room with it. Its value comes entirely from what it can be exchanged for. Hand it to someone selling a bicycle and they part with a genuinely useful object, not because they want the paper, but because they want the purchasing power it carries. They can pass it on tomorrow for a coat, or groceries, or a tank of fuel. The note is never really theirs; it is simply their turn to spend it. That shared confidence is the whole trick. As the Bank of England puts it, modern money works because people trust that others will accept it, not because anything physical stands behind it.

What is the coincidence of wants problem?

The coincidence of wants problem is the flaw at the heart of barter: a direct swap only works when each side happens to want exactly what the other is offering, at the same time. Money dissolves the problem, because a seller will take cash from anyone, confident they can spend it later on whatever they actually need.

Picture a world with no currency. Say you bake bread, a hundred loaves a day, and your ovens need coal. You walk to the fuel merchant and try to trade loaves for a sack of coal. How many loaves is a sack worth? Nobody knows, because there is no ready market for that trade. Worse, if a rival baker got there first, the merchant already has more bread than he can eat and waves you away. Now imagine offering him website consultancy instead of bread; the conversation ends faster still. Economists call this the double coincidence of wants: for a trade to happen, the baker must want coal and the coal seller must want bread, at the same moment. Money removes one side of that double requirement. The merchant does not want your bread, but he will take a note, because he can store its value and redeem it later for something he does want. The St. Louis Fed uses the same barter example to explain why every society eventually reaches for money.

What makes money good money?

Good money tends to share a handful of properties: durability, so it survives being handled and hoarded; divisibility, so it settles both tiny and enormous sums; portability, so value is easy to carry and send; scarcity, so no one can conjure more at will; and fungibility, so any one unit is interchangeable with any other.

Each property earns its place. Durability rules out anything that rots or rusts. Divisibility is why coinage came in denominations; ancient Rome minted a gold aureus worth twenty-five silver denarii, so people could pay for a loaf or a legion. Portability is why a small purse of metal beat driving a herd of cattle to market. Scarcity is the subtle one: money holds value only if the supply cannot be inflated cheaply, which is why forgery and reckless issuance are so corrosive. Fungibility means your ten-pound note spends exactly like mine. That last property survives some surprising variety. In Hong Kong, banknotes are issued by three commercial banks, HSBC, Standard Chartered and Bank of China, and they look quite different, yet each is accepted at face value as though identical. The United Kingdom is similar, with several banks in Scotland and Northern Ireland still printing their own notes alongside the Bank of England's.

What is commodity money, and why did gold win?

Commodity money is money made of something with its own usefulness: salt, cattle, shells or metal. Gold outlasted every rival because it scores well on all the properties at once. It does not corrode, it divides cleanly, it is dense enough to carry serious value in a small weight, and fresh supply grows only slowly.

The historical detours are worth knowing. Roman soldiers were partly paid in salt, a genuinely scarce and useful commodity then, and the Latin salarium is where the word salary comes from. But gold kept winning. Its supply is the clearest illustration of durable scarcity: miners add only about 1.5% to 2% to the above-ground stock each year, a figure the World Gold Council's data bears out, so no single year can flood the market. The old line captures it well: an ounce of gold bought a well-made suit two centuries ago, and an ounce still buys a decent suit today.

Metal money was not tamper-proof, though. Because early coins were crude by modern standards, they invited coin clipping, the practice of shaving a sliver of metal from each coin's edge. Skim 1% off a hundred coins, melt the shavings, and you have minted a hundred-and-first while barely marking the rest. The fix was neat: when Isaac Newton became Master of the Royal Mint in 1699, he championed milled, inscribed edges so any clipping would show. That is why UK pound coins still carry the words DECUS ET TUTAMEN around the rim, Latin for "an ornament and a safeguard", a safeguard against exactly this fraud.

Carrying gold around was inconvenient and risky, which produced the next leap. In seventeenth-century England you could deposit gold with a trusted goldsmith and receive a signed receipt for it. Make that receipt payable to whoever holds it and you have invented both the banknote and the bearer instrument: I hand you the paper, you redeem the gold. Banks formalised the role, from Sweden's Sveriges Riksbank in 1668 to the Bank of England in 1694. For a long stretch many banks issued their own notes, which carried an obvious catch. A note was only ever a claim on that bank's solvency, and America's nineteenth-century wildcat banks failed often enough to leave holders with worthless paper. The risk never fully went away. In 2023, depositors fled Silicon Valley Bank and other US regional lenders at the first sign of trouble, a reminder that a claim on an institution is only as sound as the institution.

What is fiat money, and what are its trade-offs?

Fiat money is currency a government declares valid without backing it by gold or any commodity. The upside is flexibility: the supply can bend to fit the economy. The downside is discipline, because the very power to print freely is the power to debase, and history is crowded with governments that could not resist using it.

The move to fiat was gradual and often forced by war. Britain suspended gold convertibility in 1914 under the strain of the First World War, restored it in 1925 as a matter of national pride under Chancellor Winston Churchill, then abandoned it for good in 1931 when the deflation it caused proved unbearable, the moment the Bank of England marks as the end of the UK gold standard. The United States went further and stranger. During the Great Depression, in 1933, Executive Order 6102 made private gold ownership illegal and compelled Americans to sell their gold to the government at $20.67 an ounce. Within a year the Gold Reserve Act revalued gold to $35, quietly devaluing the dollar by more than 40% against the metal citizens had just handed over.

The final break came in 1971. Under the 1944 Bretton Woods settlement, other Western currencies were pegged to a US dollar that was itself redeemable for gold at $35 an ounce. Then the Vietnam War stretched American finances, the dollar supply expanded faster than the gold behind it, and foreign governments noticed. West Germany floated its currency in May 1971; Switzerland and France began cashing their dollars in for bullion. Faced with a run on the gold reserves, on 15 August 1971 President Nixon went on television and suspended the dollar's convertibility into gold, calling the move temporary. It was permanent. From that day, the dollar and every currency tethered to it floated free of any metal, backed only by faith in the issuing government, its power to tax, and, in the dollar's case, the world's habit of pricing oil and trade in it.

Well-run fiat can hold that confidence for decades. Badly run fiat punctures it fast. The Weimar Republic printed its way into 1920s hyperinflation; Zimbabwe did much the same and ended up issuing hundred-trillion-dollar notes; Venezuela's bolivar collapsed until a loaf of bread cost a bag of cash. Fiat money always sits on this knife-edge, and over the long sweep of history almost every fiat currency has eventually failed.

Why does understanding money matter for Bitcoin?

Because Bitcoin is a direct response to fiat's central weakness. If money breaks when its issuer can print without limit, then a money nobody can print becomes worth a serious look. Bitcoin borrows gold's scarcity, hard-caps the supply at 21 million coins, removes the need to trust any mint or bank, and enforces the rules in software.

Run Bitcoin through the same checklist and the design intent is clear. It is durable, because the ledger is copied across thousands of machines. It is divisible to a hundred-millionth of a coin. It is portable enough to send across the world in minutes. Above all it is scarce by arithmetic rather than by decree, which is the property fiat gave up in 1971. This is not investment advice, and Bitcoin has real trade-offs of its own, but the motivation is hard to miss once you have followed money's history. That history is also why it emerged when it did: the Bitcoin whitepaper appeared in 2008, in the wreckage of a banking crisis, a story I tell in the origins of Bitcoin. If you want the mechanics behind the scarcity, see how Bitcoin works; if you want to know where it might lead, read the future of Bitcoin. Or start from the top of our complete Bitcoin guide.

Frequently asked questions

What are the three functions of money?

Money does three jobs. It is a medium of exchange, something everyone will accept in trade so you avoid bartering. It is a store of value, holding its worth between the moment you earn it and the moment you spend it. And it is a unit of account, a common yardstick for pricing everything else.

What is the double coincidence of wants?

It is the barter trap money was invented to escape. Under barter, a swap only happens if both people want what the other has at the same time: the baker needs coal and the coal seller needs bread. Money removes one side of that requirement, so a seller can accept cash from anyone.

Why did the world abandon the gold standard?

Mostly because war and depression pushed governments to spend beyond their gold. Britain broke with gold in 1931, and the United States severed the dollar's last link in 1971 when Nixon suspended convertibility during the Vietnam War. Once currencies floated free of metal, their supply became a matter of policy, not geology.

Is fiat money backed by anything?

Not by a commodity. Fiat currency is backed by confidence: trust in the issuing government, the legal requirement to pay taxes in it, and its usefulness in trade. That confidence can be durable when a currency is well managed, but it can also collapse quickly, as hyperinflations from Weimar Germany to Venezuela show.

Does Bitcoin count as money?

It depends which function you weigh. Bitcoin is highly divisible, portable and genuinely scarce, and a growing number of people treat it as a store of value. Its volatility still limits its use as an everyday medium of exchange and unit of account. Whether that changes is one of the open questions about its future.