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Justification, Deductive Closure and Reasons to Believe

Published online by Cambridge University Press:  13 April 2010

Robert Audi
Robert Audi
Affiliation:
University of Nebraska–Lincoln
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Extract

By deduction, we often extend both our knowledge and our justified belief. Moreover, in achieving knowledge or justified belief of some proposition, we commonly acquire justification for believing many of its entailed consequences, such as at least some of those that self-evidently follow from it. These and related facts have led some philosophers to endorse strong closure principles, for instance: If a person, S, is justified in believing a proposition, p, and p entails q, then S is justified in believing q. Others have denied such principles, whether for justification or, with the appropriate additions, for knowledge. The debate continues. There is, however, this much consensus: there are difficult problems about the scope of closure, and epistemology should develop theories that can resolve them.

Type
Articles
Information
Dialogue: Canadian Philosophical Review / Revue canadienne de philosophie , Volume 30 , Issue 1-2 , Winter 1991 , pp. 77 - 84
Copyright
Copyright © Canadian Philosophical Association 1991

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References

Notes

1 See, e.g., Klein, Peter D., Certainty: A Refutation of Scepticism (Minneapolis: University of Minnesota Press, 1981).Google Scholar

2 See, e.g., Dretske, Fred, “Epistemic Operators,” Journal of Philosophy, 67 (1970)CrossRefGoogle Scholar, and Nozick, Robert, Philosophical Explanations (Cambridge: Harvard University Press, 1986)Google Scholar. The reference to appropriate additions is mainly intended to allow for formation of the belief that q: one can be justified in believing q without believing it, and on the plausible assumption that knowing entails believing, the epistemic counterpart of the justificational closure principle stated must specify that the subject, S, believes the entailed consequence. It is also usually required that S believe it on the basis of p.

3 Alternatively we could speak of S's being justified in believing that p entails q, or of p's obviously entailing q. None of these is unproblematic, but all have some plausibility.

4 Audi, Robert, Belief, Justification, and Knowledge (Belmont, CA: Wadsworth Publishing, 1988), p. 77–78.Google Scholar

5 See Canary, Catherine and Odegard, Douglas, “Deductive Justification,” Dialogue, 28, 2 (1989): 316. References to this article below will be given parenthetically in the text.CrossRefGoogle Scholar

6 In the book I did not talk of possible worlds, but I think it is useful to do so. Such talk raises problems that cannot be addressed here, but I do not think that any of them will vitiate the discussion to follow.

7 Richard Foley suggested this reply to me in correspondence; and whether or not Canary and Odegard have it in mind in the passage, it has occurred to others as well as Foley.

8 In a paper in progress I am trying to develop a theory and a diverse set of principles to do the job.

9 The reference to understanding here avoids the implication that one can have a reason to believe a proposition one cannot understand. One could plausibly reply that one has a reason, but simply cannot see it as one. This may simply show that there are different notions of “having” a reason. There are many problems in formulating transmission principles here, and I believe that for different plausible principles we get different notions of what it is to have a reason.

10 At least one further qualification may be needed. Consider the lottery case in which S justifiedly believes S's ticket, being one of a million in a fair lottery, will lose. Arguably, there is neither a Gettier problem here nor a degree of justification that is achievable by simply increasing the number of tickets and sufficient to render S's belief knowledge if it is true.

11 I stressed this requirement of minimal justification. If absolute indefeasibility is allowed, then of course my example will not work; but only extreme epistemological theories would require that level of justification for entitlement to believe, or even for knowledge.

12 In Chapter 9 of Belief, Justification, and Knowledge, some of these principles are discussed critically, and suggestions are made for rebutting any scepticism that appeals to such possibilities as hallucinatory experiences which are intrinsically just like my present experience of seeing this piece of paper.

13 My thanks to James Sennett for helpful discussion of the topic of this paper.