Rational spirits and the post Keynesian macrotheory of microeconomics

Summary The argument that post Keynesian theory rejects rationality and maximization as a basis of agent behaviour and is thus non-rational and lacking micro-foundations is contrasted by reference to Keynes' use of his early work on probability in the General Theory. Instead of presuming rational choice over perfectly known events, post Keynesian theory builds on Keynes' explanation of agents' rational beliefs in uncertain propositions about their knowledge of the world. These rational spirits lead to the recognition of the macro constraints to individual action or a macrofoundations of microeconomics linked to the role of money and to the role of liquidity preference as both a measure of rational belief and a determinant of money prices which equate the rates of return on all existing and newly produced goods. In this equilibrium prices will generally diverge from costs of production, in contrast to perfect competition but in concordance with the post Keynesian microeconomic theories of mark-up pricing.Comments by L. Hoogduin are gratefully acknowledged. He is relieved from any responsibility for my impressionistic presentation of Keynes' views on probability.