Keynes developed his ideas in response to the economic turmoil of the Great Depression, which he believed was caused by a lack of aggregate demand in the economy. He argued that governments should use fiscal policy (such as changes in taxes and spending) to stimulate demand and help to promote economic growth. This became known as Keynesian economics.

Keynes's ideas were influential in shaping the economic policies of many governments following World War II, and his work continues to be widely studied and debated by economists today. In addition to his contributions to economics, Keynes was also a prominent figure in British politics and played a key role in the design of the Bretton Woods system of international monetary management.