Keynes Spelt Out Exactly What 'Degree of Rational Belief ' Meant in His a Treatise on Probability (1921): Correcting the Severe Errors in Courgeau (2012)

Abstract

A very, very, very severe problem has been occurring repeatedly over the last 100 years in the social sciences and philosophy, when it comes to the question of understanding the meaning of Keynes ‘s logical theory of probability and his concept of rational degrees of belief. It is the failure of commentators on Keynes’s book to have actually read the A Treatise on Probability that is an ongoing problem.

Instead of reading the A Treatise on Probability, practically all social scientists and philosophers evaluate Keynes’s contribution based on a reading of F. P. Ramsey’s 1922 and 1926 reviews ,which are combined with the introduction to the latest edition of the A Treatise on Probability, Volume 8 of the Collected Writings of John Maynard Keynes, written by Richard B. Braithwaite, who claimed that he had read the A Treatise on Probability during the break between academic terms at Cambridge University in 1921, as reported in C. MIsak’s 2020 biography of Frank Ramsey.

Given that it took the French mathematician, Emile Borel, three years to cover Part I of Keynes’s A Treatise on Probability in preparation for his 1924 review and that it took the American mathematician, Edwin Bidwell Wilson, Paul Samuelson’s mentor, 13 years before he was able to write his review of Part II of Keynes’s A Treatise on Probability in the September, 1934 issue of the Journal of the American Statistical Society, I believe that the above facts provide overwhelming evidence that Richard B Braithwaite claim can’t be sustained. It is not possible, as he claimed, to be able to read the A Treatise on Probability in less than two month’s time.

This problem shows up again repeatedly on pages 278-284 in D. Courgeau’s 2012 research manual, Probability and Social Science, where evaluations of Keynes’s work are made that have nothing to do with Keynes’s book. Misak based her assessment on individuals, such as Clive Bell, who simply would have no idea about what Keynes was talking about. When one combines such empty speculations with the impossible claims made by Braithwaite and Ramsey’s juvenile book reviews of Keynes’s A Treatise on Probability, the result is simply nonsensical, given that the fundamental differences between Keynes and Ramsey are between imprecise views of probability versus precise views of probability, respectively.