Is Vagueness Linguistic?

The central thesis of this book is:

Propositional Vagueness. Vagueness is fundamentally a property of prop­ositions, objects, and other non-linguistic entities.

Propositional Vagueness should be contrasted with the usual assumption that vague­ness is fundamentally a property of sentences, names, and other linguistic items.

Almost everyone writing on vagueness has assumed that vagueness has something to do with language. Indeed, when this assumption is not held without reservation, it is often because one wants to make room for the possibility of‘metaphysical vagueness' in addition to linguistic vagueness; few have argued that ordinary vagueness has little directly to do with language.^[31] I spell out the main differences between linguistic and non-linguistic theories of vagueness further in chapter 4.

One might think that since the epistemicist slogan is that vagueness is ignorance, and since the objects of knowledge and ignorance are propositions, epistemicism ought to maintain that vagueness is propositional and thus not linguistic. However, matters are not so clear cut, since two of the most prominent epistemicists in fact fall on the linguistic side. Timothy Williamson [156] argues that vagueness arises when a linguistic expression is semantically plastic: there are nearby worlds where slight changes in the use of the term have caused it to have a slightly different meaning. Paul Horwich [71] argues that vagueness arises for sentences in a mental language when the constitutive rules of use for that sentence preclude both its application and the application of its negation.

Most supervaluationists fall on the linguistic side of the fence, maintaining that vagueness arises when there are multiples interpretations of the language compatible with linguistic conventions (see, for example, Keefe [78]). Note, however, that not every Supervaluationist talks this way.

As may be expected, in addition to accepting the ideology of propositional vagueness I also endorse the existential claim:

Vague Propositions. There are vague propositions.

(It should be noted, by contrast, that although I maintain that the ideology of a vague object is more fundamental than that of a vague name, I'll remain for the most part neutral about whether there are any vague objects in this book. The status of vague objects is discussed further in chapter 16.)

Philosophers who take vagueness to be primarily linguistic might naturally be associated with the view that there are no vague propositions. And indeed many do have this view, maintaining that a vague sentence expresses (in some sense) an array of different but closely related precise propositions. But this association is not forced: it could be that there are vague propositions, but that sentential vagueness is the basic notion and that propositional vagueness is to be somehow explained in terms of it.

3.2