Recent developments in econometrics and economic theory attest the growing evidence of strong uncertainty. The paper argues that these developments both question seriously the methodological foundations of the mainstream macroeconomics and support Keynes's powerful concepts and theory. It emphasizes how replacing ‘risk' with strong uncertainty suffices to transform the standard four-macro-markets system into a shifting demand-driven system, with the result that price rigidity is not to be considered the cause of the effective demand leadership (although, as Keynes pointed out, some rigidity is required to give us some stability in a monetary economy). As it is not based on a restrictive definition of uncertainty, Keynes's theory is more rea...