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Does Roush show that evidence should be probable?

Fennell, D.; Cartwright, N.

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D. Fennell


This paper critically analyzes Sherrilyn Roush’s (Tracking truth: knowledge, evidence and science, 2005) definition of evidence and especially her powerful defence that in the ideal, a claim should be probable to be evidence for anything. We suggest that Roush treats not one sense of ‘evidence’ but three: relevance, leveraging and grounds for knowledge; and that different parts of her argument fare differently with respect to different senses. For relevance, we argue that probable evidence is sufficient but not necessary for Roush’s own two criteria of evidence to be met. With respect to grounds for knowledge, we agree that high probability evidence is indeed ideal for the central reason Roush gives: When believing a hypothesis on the basis of e it is desirable that e be probable. But we maintain that her further argument that Bayesians need probable evidence to warrant the method they recommend for belief revision rests on a mistaken interpretation of Bayesian conditionalization. Moreover, we argue that attempts to reconcile Roush’s arguments with Bayesianism fail. For leveraging, which we agree is a matter of great importance, the requirement that evidence be probable suffices for leveraging to the probability of the hypothesis if either one of Roush’s two criteria for evidence are met. Insisting on both then seems excessive. To finish, we show how evidence, as Roush defines it, can fail to track the hypothesis. This can remedied by adding a requirement that evidence be probable, suggesting another rationale for taking probable evidence as ideal—but only for a grounds-for-knowledge sense of evidence.


Fennell, D., & Cartwright, N. (2010). Does Roush show that evidence should be probable?. Synthese, 175(3), 289-310.

Journal Article Type Article
Acceptance Date Mar 16, 2009
Publication Date Aug 1, 2010
Deposit Date Sep 17, 2015
Publicly Available Date Sep 21, 2015
Journal Synthese
Print ISSN 0039-7857
Electronic ISSN 1573-0964
Publisher Springer
Peer Reviewed Peer Reviewed
Volume 175
Issue 3
Pages 289-310
Keywords Evidence, Philosophy of science, Probability, Surprising evidence.


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Copyright Statement
© The Author(s) 2009. This article is published with open access at Open Access. This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.

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