John Maynard Keynes is an English economist, founder of the Keynesian direction in economics. During the Great Depression of the 1930s, Keynes spearheaded a revolution in economic thinking. He argued that aggregate demand determines the overall level of economic activity. He argued that inadequate aggregate demand could lead to long periods of high unemployment. Keynes advocated the use of fiscal and monetary policies to mitigate the negative effects of economic downturns. He elaborated on these ideas in his large work, General Theory of Employment, Interest and Money, published in 1936. In the mid to late 1930s, the leading Western economies adopted Keynes' policy recommendations. Nearly all capitalist governments did so by the end of two decades after Keynes's death in 1946. Keynes participated in the development of international economic institutions created after the end of World War II. Keynes's proposals were rejected by the American delegation on a number of points. Keynes's influence began to wane in the 1970s, in part due to stagflation. In addition, Keynes created an original theory of probability based on the assumption that probability is a logical, not a numerical, ratio.