It is the mark of science and perhaps rational thought to operate with a falsifiable understanding of how the world works. So it is fair to ask economists a fundamental question: what could happen that would cause you to revise your views of how the economy operates and acknowledge that the model you had been using was 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 past 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 macroeconomy.