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Keynes's Weight of Argument and Popper's Paradox of Ideal Evidence

Published online by Cambridge University Press:  01 April 2022

Rod O'Donnell
Rod O'Donnell*
Affiliation:
School of Economic and Financial Studies, Macquarie University
*
‡Send reprint requests to the author, School of Economic and Financial Studies, Macquarie University, North Ryde, Sydney NSW 2109, AUSTRALIA.
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Abstract

Popper's paradox of ideal evidence has long been viewed as a telling criticism of Keynes's logical theory of probability and its associated concept of the weight of argument. This paper shows that a simple addition to Keynes's definitions of irrelevance enables his theory to elude the paradox with ease. The modified definition draws on ideas already present in Keynes's Treatise on Probability (1973). As a consequence, relevant evidence and the weight of argument may increase, even when new evidence leaves the probability unaltered.

Type
Research Article
Information
Philosophy of Science , Volume 59 , Issue 1 , March 1992 , pp. 44 - 52
Copyright
Copyright © Philosophy of Science Association 1992

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Footnotes

†

This paper is based on an earlier account given in O'Donnell (1989b). I should like to thank Alan Chalmers for his helpful comments; King's College, Cambridge, for permission to quote from the Keynes Papers; and the Australian Research Council for assistance with funding.

References

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