Fundamentally, the refutation of Say's Law by Keynes' General Theory (GT) depends on two elements: the uncertainty is necessary, but not enough. The full refutation of that law also depends on an asset which has the essential properties described and analyzed by GT. Uncertainty and money (as a liquid asset) allow the system an equilibrium with involuntary unemployment. Therefore, economic policy has a logical role on the system and economic analysis receives new methodological and dynamic elements. Instability and irrevocability reach place in economic theory. This article regards these considerations, from a post-keynesian perspective.
Say's Law; Keynes; uncertainty; instability; irrevocability