Problems of Precision in Bayesian Epistemology and Fuzzy Theories of Vagueness

Nicholas J. J. Smith (University of Sydney)

A common objection to theories of vagueness based on fuzzy logics centres on the idea that assigning a single numerical degree of truth – a real number between 0 and 1 – to each vague statement is excessively precise.  A common objection to Bayesian epistemology centres on the idea that assigning a single numerical degree of belief – a real number between 0 and 1 – to each proposition is excessively precise.  In this talk I explore possible parallels between these objections.  In particular I argue that the only good objection along these lines to fuzzy theories of vagueness does not translate into a good objection to Bayesian epistemology.  An important part of my argument consists in drawing a distinction between two different notions of degree of belief, which I call dispositional degree of belief and epistemic degree of belief.