It’s not just Keynesianism that’s under a cloud. The same fate has befallen monetarism — the doctrine that stable growth in the money supply can promote a more stable economy. Since 2008, the Federal Reserve has poured more than $3.2 trillion into the economy to keep interest rates low and accelerate economic growth. By monetarist reasoning, so much money pumped out so quickly should spawn higher inflation. Some economists predicted as much; it hasn’t happened yet. Consumer prices today are up a mere 1.5 percent from a year earlier.

If you add the last six years of U.S. budget deficits and the Fed’s injection of cash into the economy, the total is approaching $10 trillion. It’s hard to believe that all this stimulus didn’t aid the recovery, but the fact that it resulted in only modest growth has created an identity crisis for economists. The promise they held out was that, through suitable economic policies, they could produce long periods of stable growth and — just as important — avoid prolonged slumps and lengthy periods of substandard growth. Clearly, they aren’t delivering on this promise.

The Great Recession and financial crisis changed behavior in fundamental ways that economists have yet to incorporate fully into their models or theories. The widespread faith that modern societies were sheltered from deep and sustained economic setbacks has been shattered, causing consumers, business managers and bankers to be more cautious in borrowing and spending. Economic stimulus may offset this caution, but if it signals that the economy is weaker than expected, it may also further depress private spending. There are countervailing tendencies.