Equilibrium is an organising principle of economic thinking subject to incompatible interpretations. The idea of a Keynesian equilibrium as a position of rest with involuntary unemployment contrasts with Pasinetti's notion of an equilibrium situation, that is, an unstable position with full employment. In the former, an equilibrium state cannot be separated from the mechanisms that may (or may not) lead to it, whereas in the latter, the explicit separation between both layers is crucial.

This chapter explores how Pasinetti's methodological standpoint, formulation of the principle of effective demand and conceptualisation of equilibrium, cumulatively build up into a scheme of structural dynamics. It is argued that compositional changes in the structure of demand and the uneven pace of productivity increases render equilibrium situations impossible to maintain through time, especially as regards (full) employment. Therefore, rather than seeking explanations as to why the economy does not return to its equilibrium path, it proves fruitful to specify and empirically implement computable norms to quantify how far (or close) actual economies are from them, providing a compass for policy.

Thomas Roberts Malthus is typically considered a ‘classical’ economist together with Adam Smith and David Ricardo. However, in important respects his view differed fundamentally from theirs, as Keynes emphasised in his biographical essay on Malthus. Most importantly, Malthus vehemently opposed Ricardo’s doctrine that it was impossible for effective aggregate demand to be deficient. Keynes, who also insisted on the possibility of effective demand failures, therefore considered Malthus to have been a precursor of his own view. The chapter discusses the following themes. What was the classical conception of ‘Say’s law’ and what were the reasons why Ricardo endorsed and Malthus rejected it? What were the main lines of reasoning in the ‘general glut’ controversy between Malthus and Ricardo? Was Keynes justified in considering Malthus’s doctrine to foreshadow his own doctrine, and if not, why not? What are the reasons why according to Pasinetti the classical (Ricardo-Sraffa) approach to the theory of relative prices and income distribution is compatible with Keynes’s principle of effective demand?