Keynesian economics is the economics of nominal rigidities basically, nominal rigidities everywhere. Fully anticipated money does affect output. Ever… - Alan Blinder

First and foremost, Keynesian economics is a theory of aggregate demand and of the effects of aggregate demand on real output and inflation.

Economists have the least influence on policy where they know the most and are most agreed; they have the most influence on policy where they know the least and disagree most vehemently.

For a period of roughly 35 years, Keynesian theory provided a central paradigm for macroeconomists, and considerable progress was made on several empirical fronts. It was widely recognized that some of the ingredients of Keynesian economics (e.g. money illusion and/or nominal wage rigidity) rested on slender to non-existent microtheoretic foundations; and there were always dissenters. But, thought of as a collection of empirical regularities that fit together into a coherent whole, the theory worked tolerably well. In the 1970s, however, the Keynesian paradigm was rejected by a great many academic economists, especially in the United States, in favour of what we now call new classical economics. By about 1980, it was hard to find an American academic macroeconomist under the age of 40 who professed to be a Keynesian. That was an astonishing intellectual turnabout in less than a decade, an intellectual revolution for sure.