Tolerance and Degrees of Truth

This paper explores the relations between two logical approaches to vagueness: on the one hand the fuzzy approach defended by Smith (Vagueness and degrees of truth. Oxford University Press, Oxford, 2008), and on the other the strict-tolerant approach defended by Cobreros et al. (“Tolerant, Classical, Strict”, J Philos Logic 41(2):347–385, 2012). Although the former approach uses continuum many values and the latter implicitly four, we show that both approaches can be subsumed under a common three-valued framework. In particular, we defend the claim that Smith’s continuum many values are not needed to solve what Smith calls ‘the jolt problem’, and we show that they are not needed for his account of logical consequence either. Not only are three values enough to satisfy Smith’s central desiderata, but they also allow us to internalize Smith’s closeness principle in the form of a tolerance principle at the object-language. The reduction, we argue, matters for the justification of many-valuedness in an adequate theory of vague language.