One of the reasons which make the Keynesian controversy still so live, is the missing distinction between aspects concerning methodology and others pertaining to theory. Another cause of the ongoing debate is to be found in unsettled problems concerning methodology, in primis the concept the equilibrium. Nor could the situation have been different, given, on the one hand, Keynes's manifest disaffection with these matters (especially in The General Theory) and, on the other hand, their implications as regards Keynesian economic theory and policy. The aim of this volume ensues from this analysis; accordingly, a wide spectrum of questions of method are considered and different interpretations of Keynes's approach in this field are taken into consideration.