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

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.

The new arguments for rules take an entirely different tack. They are based neither on the ignorance nor the knavery of public officials and, in fact, assume that everyone knows how the economy operates—even the government! Moreover, the government's objectives are assumed to coincide with the people's objectives, and everyone has rational expectations. Despite these seemingly ideal circumstances, modern critics argue that a central bank left with discretion will err systematically in the direction of excessive inflation. To remedy this distortion, they advocate a fixed rule.

The word ‘Keynesian’ means many things to many people. Decades ago, it was a carelessly applied label for economic liberals and interventionists in general. For a while in the late 1970s and early 1980s it became a pejorative term more or less synonymous with old-fashioned.