It is the mark of science and perhaps rational thought more generally to operate with a falsifiable understanding of how the world operates. And so it is fair to ask of the economists a fundamental question: What could happen going forward that would cause you to substantially revise your views of how the economy operates and to acknowledge that the model you had been using was substantially flawed? As a vigorous advocate of fiscal expansion as an appropriate response to a major economic slump in an economy with zero or near-zero interest rates, I have for the last several years suggested that if the British economy - with its major attempts at fiscal consolidation - were to enjoy a rapid recovery, it would force me to substantially revise my views about fiscal policy and the workings of the macroeconomy more generally.
Summers, Lawrence H. "Why the UK Must Reverse its Economic Course." Reuters, September 17, 2012.