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Richman on the Principle of Deducibility for Justification

Published online by Cambridge University Press:  01 January 2020

G. W. Fitch*
Affiliation:
Arizona State University

Extract

In a recent paper Robert J. Richman joins a host of doubters who question Gettier's claim that knowledge is not justified true belief. Richman's scepticism of Gettier's counterexamples to the traditional analysis of knowledge stems from what he says are two basic defects in the examples. One defect is that Gettier employs the Principle of Deducibility for Justification (PDJ) which Richman argues is false. The second defect is based on “the obvious consideration that a belief which is justified on the basis of one set of facts or assumptions need not be justified on the basis of a different set.” I shall consider each of these alleged defects and argue that Richman has not shown that in fact they are defects and that Gettier's counterexamples (or a modified version of them) do in fact show that knowledge is not justified true belief.

The Principle of Deducibility for Justification states that for any proposition P, if P entails Q and S correctly deduces Q from P and accepts Q as a result of this deduction, then Sis justified in believing Q.

Type
Research Article
Copyright
Copyright © The Authors 1976

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References

1 “Justified True Belief as Knowledge” Canadian Journal of Philosophy IV No.3, March 1975.

2 lbid.p. 437.

3 Ibid. p. 436.

4 Ibid. pp. 436–437.

5 Ibid. p. 438.

6 “An Alleged Defect in Gettier Counterexamples” The Australasian journal of Philosophy LII No. 1, May 1974.

7 In his paper Why I Know So Much More Than You Do,American Philosophical Quarterly IV (1967), Rozeboom, William W.Google Scholar suggests that S is justified in “absolutely believing” P on the basis of e only if e necessitates P. If one accepts Rozeboom's necessary condition for justification of absolute belief (which he claims is needed for knowledge), then Gettier's counterexamples will not work. However, Rozeboom's condition is so strong that it rules out all practical cases of knowledge, as he points out at the end of his paper. In any case Rozeboom's position will not affect my arguments against Richman.