This paper examines some of the challenges raised by Joan Robinson in constructing a Post-Keynesian economic theory, with the intent to provide some assessment of their relevance today. Rather than dwell on her criticisms of neoclassical economics and of the Neoclassical synthesis, on which much has already been written (even though, unfortunately, not taken on board by mainstream economics), the focus here is on her arguments on how to construct a Post-Keynesian economic theory, possibly now forgotten or at any rate neglected. It is argued that there is still much to be learnt by reviving them today.