Abstract
Why should coherence be an epistemic desideratum? One response is that coherence is truth-conducive: mutually coherent propositions are more likely to be true, ceteris paribus, than mutually incoherent ones. But some sets of propositions are more coherent, while others are less so. How could coherence be measured? Probabilistic measures of coherence exist; some are identical to probabilistic measures of confirmation, while others are extensions of such measures. Probabilistic measures of coherence are fine when applicable, but many situations are so information-poor that the requisite probabilities cannot be determined. To measure coherence in these cognitively impoverished situations, this article proposes that the discussion be broadened to include plausibilistic measures of coherence. It shows how plausibilistic measures of coherence can be defined using plausibilistic measures of confirmation. It then illustrates how plausibilisic coherence can be measured in situations where probabilistic coherence cannot be determined. The coherence values obtained through the use of plausibilistic measures are often, though not always, comparable. The article also shows that coherence can be instantiated on different levels, one of which permits connections to inductive strength and deductive validity.
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Notes
I have adapted Chu and Halpern’s set-theoretic statement to the propositional idiom.
Terminology varies. Bovens and Hartmann actually use the term ‘quasi-ordering’ to describe a relation that is reflexive, transitive, but not necessarily complete (2003, p. 25).
This restriction is inessential. Logically equivalent and contradictory propositions could be included by stipulating that the conditional plausibility of equivalents is the maximal value \(\top \) and that of contradictories is the minimal value \(\bot \).
I am greatly indebted to an anonymous reviewer for this point.
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Welch, J.R. Plausibilistic coherence. Synthese 191, 2239–2253 (2014). https://doi.org/10.1007/s11229-013-0395-9
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DOI: https://doi.org/10.1007/s11229-013-0395-9