I 1921 1921 Yasuhiro Sakai / J M 1921 365 100 20 probability uncertainty J M Keynes, 1883-1946 1936 The General Theory of Employment, Interest and Money 1921 A Treatise on Probability 050 2013 winter / No.398
silver spoon Frank H. Knight, 1885-1972 wooden spoon 1921 Risk, Uncertainty and Profit 1921 1921 the miracle year of 1921 1935 The Ethics of Competition Milton Friedman Homer Jones George StiglerAllen Wallis 49 1920 30 1 1 2012 051
7 26 II 1 probability favorable cases to the whole number of cases possible probability 3 50 probability probability theory A Treatise on Probability 2 PROBABILITY source: Oxford Dictionary of English noun the quality or state of being probable; the extent to which something is likely to happen or be the case. [mathematics] the extent to which a event is likely to occur, measured by the ratio of the 2 1921 1921 2 probability 1989 probabilities Borel 1938 1965 052 2013 winter / No.398
1921 15 O A O A 1 1 O impossibility I certainty A O I numerically measurable probability U, V, W, X, Y, Z nonnumerical probabilities VA W, X Y X Y W V A V Z W, X, Y U V, W, X, Z 053
2 O A I O 0 A 60 I O 0 100 OAI I 100 A 60 3OVWXI U V 30 40 V 30 40 3 30 40 45 65 50 80 W 45 65 X 50 80 45 65 50 80 Y W Z W W45 65 X50 80 3 W X 1 4 VA VAW A 1 partial order O A O A X A 30 4060 45 65 60 50 80 60 5OZWYI W Z Y W W A Z A 3 interval valued probability Keynes 1921, p.161 Brady 2004 054 2013 winter / No.398
X A Z65 W 45 65 Y45 Z W W Y 6 OUI 0 100 3 2030 1907 1908 1914 1 1921 1913 1919 15 1995 practical man 055
the degree of belief 32 4 66 1 2 1909 1908 4 3 1 25 26 4 700 4Gillies 2000 2011 056 2013 winter / No.398
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5 4 2 4 1936 1 2 1921 1936 100 6 156 5 Skidelsky 2009 2007 058 2013 winter / No.398
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20 1950 40 1970 1989 100 1868 1912 1872 1928 5 161 animal spirits 161 060 2013 winter / No.398
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J. M. Keynes' Theory of Probability versus F. H. Knight's Theory of Uncertainty: Reflections on the Miracle Year of 1921 Yasuhiro Sakai The main purpose of this paper is to critically discuss and lucidly compare J. M. Keynes (1883-1946) and F. H. Knight (1886-1972), two towering figures in the history of economic thought. It is in 1921 that they both published apparently similar books on risk, probability and uncertainty. While Knight contribution on the economics of risk and uncertainty has been well-known and very influential in the economics profession, Keynes accomplishments on probability and uncertainty have been more or less underestimated in the dark shadow of his most famous book (1936) The General Theory of Unemployment, Interest and Money. The present paper aims to focus on an earlier yet equally important book (1921) A Treatise on Probability, hopefully shedding a new light on his outstanding ideas and everlasting influences on his later works including The General Theory. According to Keynes, many probabilities, which are incapable of numerical measurement, can be placed nevertheless between numerical upper and lower limits. Keynes has demonstrated whether and to what extent animal spirits contributes to the working and performance of the market economy. Remarkably, Keynes' concept of probability and uncertainty can be well-compared to Knight's distinction between a measurable risk and a non-measurable uncertainty. I believe that it is high time for us to unify Keynes and Knight into a new, comprehensive approach to very complex human behavior. 068 THE HIKONE RONSO 2013 winter / No.398
J. M. Keynes' Theory of Probability versus F. H. Knight's Theory of Uncertainty Yasuhiro Sakai 069