Keynes's theories of the business cycle: evolution and contemporary relevance.

This paper examines the development of John Maynard Keynes's theory of the business cycle from his early writings in 1913 through the 1940s, identifying six distinct theoretical stages. Throughout these stages, the central driver of economic fluctuations remained cyclical changes in expectations about future returns, with the banking system playing a crucial role in financing and shaping these expectations. Keynes's evolving frameworks addressed the saving–investment relationship, the banking system's influence, the effectiveness of monetary policy (notably short-term interest rate control), and the increasing importance of fiscal and investment policies to moderate fluctuations. The paper highlights Keynes's consistent emphasis on uncertainty and fragile knowledge underpinning investment decisions, and concludes that his integrated policy mix—combining monetary and fiscal tools—retains relevance for contemporary macroeconomic stability.