Financial markets have a nasty habit of proving eminently logical decisions utterly wrong.

Take the 1999 decision by Gordon Brown, the British Finance minister at the time, to sell more than half his government’s gold reserves. The right of currency holders to turn paper into gold at central banks had long since ceased — ending gold’s special position as a form of reserve currency and removing an essential reason for governments to keep it. All things considered, Lenin’s famous suggestion that all gold should be melted down to build....