John Maynard Keynes (1883–1946)

To understand Keynes’s revolutionary contributions to economics it is important to remember that though he read mathematics at Cambridge as an undergraduate, he spent as much time on philosophy, and subsequently became an original philosopher in his own right. His first major publication, A Treatise on Probability (1921), was on philosophical issues; it was originally written in 1908–9 as a Fellowship dissertation for King’s. Though he was to respond to criticism of it, especially by Frank Ramsey, it nevertheless continued to provide the base for all aspects of his intellectual work. For his thinking about economics he took three lasting lessons from his philosophical understanding; first, the argument that there is a whole spectrum of languages, running continuously from intuition and poetry to mathematics and formal logic, all of which may be relevant at appropriate steps in arguments and for particular issues, or aspects of issues, in economics. Second, there was his realisation that in a discipline such as economics the whole may be more than the sum of the parts, a realisation he came to long before he wrote The General Theory, in which, of course, it played a crucial role. Third, Keynes thought of probability as a form of objective belief and of uncertainty as an absence of probabilistic knowledge — ‘we simply do not know’ (see Lawson, 1993).