Keynes's principle of effective demand reconsidered : the core of of a heterodox post-Keynesian paradigm, or a fundamentalist Keynesian concept that should be abandoned?

Keynes's Principle of Effective Demand is widely recognized not only as a major theoretical innovation but also as one of the core concepts uniting various post-Keynesian strands. However, Keynes's own treatment of the Principle of Effective Demand - known as the Z/D model and identified by himself as central to his attempt to fundamentally refute Say's Law - has been ignored or even outright rejected by many post-Keynesians on the grounds that it remains too deeply rooted in mainstream economics. This paper addresses such criticism by emphasizing that any evaluation of the Z/D model must take into account the paradigmatic shift Keynes sought to initiate.