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Reason and Consistency

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Analysis and Metaphysics

Part of the book series: Philosophical Studies Series in Philosophy ((PSSP,volume 4))


Is inconsistency ever reasonable? It may be reasonable for a person to accept each statement in an inconsistent set because it is reasonable, though incorrect, for him to think the set of statements is consistent. Moreover, it may even be reasonable for a person to accept a set of statements he is certain is inconsistent. A person who has discovered that he accepts an inconsistent set of statements may reasonably continue to do so when, for lack of time or insight, he sees no sarisfactory way of extricating himself. Such reflections put inconsistency in a better light than is customary. The conviction remains: there is something unreasonable about inconsistency. The question is when inconsistency is unreasonable and why it is so.

Work on this paper was supported by a grant from the National Science Foundation. An earlier version was presented at the Pacific Coast Division Meeting of the American Philosophical Association, San Francisco, 1972. Gilbert Harman commented on the paper, and his criticisms have greatly influenced the present version. I have also benefitted from discussion with Lewis Beck, Milton Jones, Henry E. Kyburg, Jr., Rolf Eberle and Roderick Chisholm.

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  1. Søren Kierkegaard, A Kierkegaard Anthology,Robert Bretall (ed.), Modern Library, New York, 1936, pp. 125–38, p. 220.

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  2. Roderick Chisholm, Theory of Knowledge,Prentice Hall, Englewood Cliffs, 1966, pp. 21–22.

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  3. Wilfrid Sellars suggests that it is ideally reasonable to accept a statement if and only if it is true, implying thereby that the set of statements it is reasonable to accept would be consistent, in ‘Are There Non-Deductive Logics?’, in Essays in Honor of Carl G. Hempel, Nicholas Rescher et al., eds., D. Reidel, Dordrecht, 1970, p. 96. Jaakko Hintikka, treating consistency as immunity from criticism, assumes that a reasonable person would alter what he accepts when shown to be inconsistent in Knowledge and Belief. An Introduction to the Logic of the Two Notions, Cornell University Press, Ithaca, 1962, p. 31. The most important article devoted exclusively to this topic is Marshall Swain, ‘The Consistency of Rational Belief’, in Induction, Acceptance, and Rational Belief, D. Reidel, Dordrecht, 1971.

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  4. I have assumed inconsistency renders a person subject to criticism in a number of articles, most recently in ‘Relevant Deduction and Minimally Inconsistent Sets’, Philosophia 3 (1973), 164, and in ‘Induction, Rational Acceptance, and Minimally Inconsistent Sets’, forthcoming in Minnesota Studies in the Philosophy of Science. The assumption is, I believe, warranted in application to the special problem of inductive inference dealt with in these papers. See also Hintikka, Knowledge and Belief,p. 31, and Leonard J. Savage, The Foundations of Statistics,John Wiley and Sons, New York, 1954, pp. 20–21. This is, however, a small sample from among those philosophers and other scholars who have claimed that a person who is inconsistent is subject to criticism on such grounds.

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  5. The Lottery Paradox was first formulated, as far as I can discover, by H. E. Kyburg, Jr., Probability and the Logic of Rational Belief, Wesleyan University Press, Middletown, 1961, p. 197.

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  6. This ideal is suggested by Sellars, ‘Are There Non-Deductive Logics?’ op. cit., p. 96. It is discussed by Keith Lehrer, ‘Reasonable Acceptance and Explanatory Coherence: Wilfrid Sellars on Induction’, Noûs 7 xxx 92–93.

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  7. I explore the relation of probability and informative content in more detail in ‘Belief and Error’, in The Ontological Turn,M. S. Gram and E. D. Klemke, eds., University of Iowa Press, Iowa City, 1974. References to earlier work by Isaac Levi, Jaakko Hintikka, Risto Hilpinen, and J. Pietarinen are given in that article (available from the author).

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  8. See Yehoshua Bar-Hillel and Rudolf Carnap, ‘Semantic Information’, The British Journal for the Philosophy of Science 4 (1953–54), pp. 145–57, and Jaakko Hintikka, ‘The Varieties of Information and Scientific Explanation’, in Logic, Methodology and Philosophy of Science, Vol. III, B. Van Rootselaar and J. F. Stall, eds. North-Holland, Amsterdam, 1968, pp. 311–332.

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© 1975 D. Reidel Publishing Company, Dordrecht-Holland

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Lehrer, K. (1975). Reason and Consistency. In: Lehrer, K. (eds) Analysis and Metaphysics. Philosophical Studies Series in Philosophy, vol 4. Springer, Dordrecht.

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  • Print ISBN: 978-90-277-1193-9

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