The economic orthodoxy that swept the world in the 1990s and 2000s attests to the terrifying power of ideas. Economists built “general equilibrium” models that, underneath all the fancy math, just assumed markets are stable and optimal. The models concluded — in a sort of “divine coincidence,” as the MIT economist Olivier Blanchard and a colleague quipped — that if central banks merely maintained steady, low inflation, they would achieve economic stability and the best growth possible. Washington and London espoused this orthodoxy. The Treaty on European Union practically inscribed it in law.