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Explanationists about epistemic justification hold that justification depends upon explanatory considerations. After a bit of a lull, there has recently been a resurgence of defenses of such views. Despite the plausibility of these defenses, explanationism still faces challenges. Recently, T. Ryan Byerly and Kraig Martin have argued that explanationist views fail to provide either necessary or sufficient conditions for epistemic justification. I argue that Byerly and Martin are mistaken on both accounts.

William Roche and Elliott Sober argue that explanatoriness is evidentially irrelevant. This conclusion is surprising since it conflicts with a plausible assumption—the fact that a hypothesis best explains a given set of data is evidence that the hypothesis is true. We argue that Roche and Sober’s screening-off argument fails to account for a key aspect of evidential strength: the weight of a body of evidence. The weight of a body of evidence affects the resiliency of probabilities in the light of new evidence. Thus, Roche and Sober are mistaken. Explanatoriness is evidentially relevant.