We witnessed that rarest of things last week—a politician's public humility. When France, along with Germany, reported an unexpected uptick in economic growth for the second quarter, French Finance Minister Christine Lagarde called the return to growth "very surprising." Imagine that—a major global economy stops shrinking, without the benefit of trillion-dollar stimulus packages or major reforms, and a politician doesn't rush to claim credit for the achievement.

Politicians don't "grow" an economy like a vegetable garden,...