What Is Money?

01 · Concept — what problem does it solve?

Before money, trade meant barter — and barter needs a double coincidence of wants: you have eggs, want shoes, and must find a cobbler who happens to want eggs. Money solves that by being a thing everyone accepts. Economists define it by three jobs it must do at once: a medium of exchange (everyone takes it), a store of value (it holds worth over time), and a unit of account (a common yardstick for prices). Anything that does all three is money — gold once, paper dollars now, and, crypto argues, a supply-capped digital asset next.

02 · Mechanics

• Commodity money has value on its own (gold, silver, grain) — worth something even with no government behind it.
• Fiat money has no intrinsic value; a dollar bill is paper. It works because the state declares it legal tender and everyone agrees to accept it — money is a shared belief.
• Supply is controlled by central banks (the Federal Reserve) via monetary policy. There is no human in the loop for Bitcoin: its supply schedule is fixed in code, capped at 21 million.
• Inflation is the erosion of the store-of-value job: when the money supply grows faster than goods, each unit buys less.

03 · Formulas

// the Rule of 72 — years for prices to double at inflation rate i
years_to_halve_purchasing_power ≈ 72 / i
// at 4% inflation: 72 / 4 = 18 years for $100 to buy ~$50 worth

// US CPI, May 2026: ~+4.2% YoY (Fed target: 2%)
// Bitcoin hard cap: 21,000,000 BTC (~19.8M already mined)

04 · Edge cases & risks

• Volatility breaks the unit-of-account job — Bitcoin can store and move value, but few price a coffee in BTC because it swings too much day to day. Stablecoins exist precisely to be the unit of account crypto otherwise lacks. See Stablecoin Design.
• Fiat isn't doomed, mismanagement is — hyperinflations (Weimar, Zimbabwe) are failures of discipline, not proof that paper money must fail. The crypto pitch is credible scarcity, not that dollars are worthless.
• "Backed by nothing" cuts both ways — fiat is backed by trust in a government; Bitcoin by trust in code and a network. Both are confidence games; they just locate the trust differently.