The Historical Importance of Keynes' A Treatise on Probability A visiting speaker in Economics recently happened to mention that John Maynard Keynes' A Treatise on Probability revolutionized probability theory. I have not heard any such claim before and it struck me as strange. The Wikipedia page contains some effusive praise from Russell but nothing specific. This leads me to ask: 1) Is this claim approximately true? 2) In what specific ways did it impact probability theory? 3) What are some specific citations which demonstrate this?

If you have a copy of Kai Lai Chung's Elementary Probability Theory, you will find Keynes' picture next to that of Kolmogorov, Polya, Feller and other probability heavy weights. (I do not know if you would cosider this evidence.) According to my modest understanding, Kolmogorov formalized probability theory and practically re-wrote the field. As far as I know he provided the framework to study probability in a measure theoretic sense. Keynes was influential not in a mathematical sense, but in a philosophical sense. A situation that exemplifies his struggle between quantifiable probability and reality is that if you have a fair coin and toss it 20 times, say you get 15 heads in a row, it would be natural to argue the coin is not fair.