Sraffa’s prices of production understood in terms of Keynes’s state of short-term expectation

Joan Robinson argued that it is the task of Post-Keynesians to reconcile the work of Keynes and Sraffa. The central difficulty is to reconcile equilibrium with uncertainty and the solution lies within Keynes’s distinction between short-, medium- and long-term expectation and furthermore between the long term and the technical long period. Recognition that the ‘expectations’ of Keynes’s state of short-term expectation are equilibrium prices, in a carefully defined and qualified sense, makes it possible to replace his Marshallian concept of normal prices with Sraffa’s prices of production. There is a definite case for seeking to recast the principle of effective demand without the Marshallian theory of value. The task is to achieve this without losing either an empirically useful concept of equilibrium or the concept of fundamental uncertainty.