"Of course the developments since then have been a great fluctuation of interests. For a long period, economics was dominated by a macroeconomic approach that in a sense was formulated by John Maynard Keynes and his revival of an era, as I regarded it, of an erroneous belief in the dependence of employment on aggregate demand, which I thought I had already finally refuted. This form of Keynesianism — which encompassed the belief that there was an unambiguous, statistically demonstrable function or connection between aggregate demand and employment — has dominated the field for the last thirty years. I found that in order to defend my conclusions concerning economic policy, which I derived from my knowledge of economics, I had to devote a lot of time to what is regarded as a scientific method — to the problems of which approach to economics leads to correct results and which leads to wrong results."