An Interpretive Theory of Vagueness

I outline an interpretive theory of vagueness, emphasizing its advantages as a theory of language in use, compatibility with the data of descriptive linguistics, and its explanation for the interest-relativity of vagueness. Central to the theory is the notion that a 'language' in the usual sense is not a well-defined object but a cluster of more or less similar sound-meaning mappings which speakers and interpreters choose among in concrete circumstances to achieve particular communicative goals. Vagueness is argued to be located not in the expressions of any particular sound-meaning mapping, but in the range of such mappings available as interpretive theories in a particular communicative situation. This approach has several advantages: it is derived from an independently motivated theory of interpretation; it explains the interest-relativity of vagueness noted by Graff (2000) without stipulation; and it provides an account not only of how but also of why some predicates are vague and others are not. Williamson (1994) explains vagueness as an epistemic phenomenon: speakers have only inexact knowledge of their language. Williamson assumes a strong form of semantic externalism according to which a language is an external object of knowledge for speakers, so that, for instance, " [t]he thoughts and practices of speakers of English establish that the truth condition for 'Harry is bald' is that Harry is bald… " (1997, p. 217). Thus the character of a speaker's language is fully determined by facts about his linguistic community, which is assumed to be a well-defined object. Lassiter (2008) argues that this type of strong externalism is incompatible with the findings of descriptive linguistics that language variation is typically gradual, that linguistic communities cannot be defined with any precision, and that normal usage is subject to considerable variation. In other words, a 'language' in Williamson's sense is a prototypically vague object, unable to fulfill the demands he places on it. As an alternative, Lassiter proposes a theory of interpretation motivated by facts about code-switching and sociolinguistic accommodation. He argues that a 'language' is a cluster of sound-meaning mappings whose precise composition can vary considerably from situation to situation, and that partial and shifting overlap between a speaker's intentions and a listener's interpretive theory is the norm. The account of vagueness that I will explore is an epistemic theory of sorts, beginning with this hypothesis: vagueness is not incomplete knowledge of a precisely defined common language, but incomplete knowledge of the intended …