This lecture will examine what we have learned and how we should change our thinking about monetary policy strategy in the aftermath of the 2007-2009 financial crisis. It will start with a discussion of where the science of monetary policy was before the crisis and how central banks viewed monetary policy strategy. It will then examine how the crisis has changed the thinking of both macro/monetary economists and central bankers. Finally, it looks at how much of the science of monetary policy needs to be altered and draws implications for monetary policy strategy.