There are vague sentences. Where does ``the vagueness of them" come from? Maybe it comes from the vagueness of the sentences' constituents: this thought would be inspired by the compositionality of sense (and the determination of reference by sense).
On the other hand, vagueness might, like truth-value, be a feature of whole sentences only. One does not attempt to trace e.g. the falsity of sentences to the falsity of one of their constituents (except in the unusual case that the sentence is a conjunction of smaller sentences.) Finally, vagueness might only be a feature of whole sentences in context: see Contextualism about Vagueness.
Sorensen's strategy in his paper is to argue for epistemicism indirectly. What epistemicism says is that vagueness is a certain kind of ignorance with regard to a sentence: it is in the mind of the person who considers the sentence. So it is not a feature of the sentence itself, the sentence at a context, or any of the individual constituents of the sentence (except insofar as my ignorance can be traced to a particular troubling predicate or individual that the sentence uses.) The kind of sentence he considers is identity sentences. This is not because identities are necessary if true (though they are necessary if true) but because identity is ``precise."*
[*I don't really know what this comes to and I am somewhat suspicious of the whole idea. Perhaps it is merely this: identity doesn't admit of borderline cases---where ``borderline case" is not the same as ``contingent case."]
Anyway, Sorensen's argument proceeds by presenting identity sentences where vagueness can be located neither in the sense, nor in the referent of any of the terms. The vagueness of the sentence, then, is independent of the sentence itself. It must be in the distinctive type of ignorance that prevents us from knowing the truth-value of the sentence.
How do we show that the vagueness of the chosen sentence, e.g. ``Acme = Sumo", is not located in the sense or in the referent of any of the terms? (This involves eliminating a lot of possibilities!)
(1) Although it is vague what ``Acme" refers to, this cannot be blamed on anything appearing in the sentence, because the sense which determines the referent does not appear in the proposition. This is the trick of the Dthat's. If the terms in the sentence have any referents at all, they are, in Kaplan's terms, ``pre-loaded":
Acme = Dthat[the first tributary of the river Enigma]
To one who replies that perhaps `Acme' has no referent, Sorensen replies that it must, for two reasons: (i) the disjunction ``Acme is Sumo or Wilt is Sumo" is definitely true; (ii) we can know things about Acme, such as ``Acme is brackish," in virtue of knowing that both Wilt and Sumo are brackish. [reply: wouldn't we think we knew that Acme was self-identical, even if it didn't exist?]
(2) The identity relation does not admit of borderline cases [is this right by the epistemicist's own lights? There is at least one mode of presentation under which the identity relation refuses to admit of borderline cases. But this isn't enough to establish the thesis---unless the epistemicist's idea is that admitting of borderline cases is admitting of borderline cases when conditions are epistemically optimal.]
(3) The only objects in the sentence are riverine bodies, and ``We are [simply] not tempted" here to ascribe the vagueness to the vagueness of these riverine bodies (although, I suppose, they might be vague anyway---can't step in the same one twice, etc.) I would not want to stake a case for the existence of vague objects on a case like this.
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What to make of this from my own vague-o-phile point of view? I just don't think this approach--starting first and foremost with vague sentences and then looking for a suspect to fix the vagueness on--is very profitable. After all, it does not seem to me that sentences are the primary locus of vagueness. The phenomenology of vagueness is something that strikes us when we look at continua: color continua, height spectra, etc. So it is, for example, a feature of color, and only derivatively a feature of sentences with color predicates. At the level of sentential form, we don't have enough information to determine whether ``Tim is pink" is vague. What we need is to see Tim, and to see his color.
There also seems to be a threat of the different views sliding past each other: vague-o-philes generally prefer sentences of the form ``a is part of b." (Let's say it's vague whether this sentence is true. At least on the notion of parthood inherited from mereology, this notion does not admit of borderline cases. Therefore the vagueness ``must be located" in a itself or b itself.) This shares with the above approach a desire to root out the vagueness of a sentence by quarantining it in one of the sentence's terms. But the two approaches want to focus on two different types of sentences: the first on the form `a = b' and the second on the form `a is part of b.' Prima facie, anyway, each side could be right about its pet sentence-type.
The ``phenomenology first!" response goes like this: we should NOT be looking first and foremost at sentence-types (or sentence-schemata?). We should be looking at the paradigm phenomenology of vagueness. What the phenomenology of vagueness tells us that some predicates (like ``blue," ``tall") are vague, while other predicates (like ``self-identical," ``taller than six feet") are not. So when we turn our attention to vague sentences of the form `Fa,' we should be mindful of the difference that the concrete value of F makes.
Likewise for vague objects. It doesn't really tell us anything to know that the form of the sentence we are studying is ``Fa" or ``a = b" or ``a is part of b". What we conclude, especially in matters of vagueness, may well depend on which a or b is at issue.
Perhaps this complaint is a bit like the contextualist's: it says that we need to know more about how the particular sentence is situated. It is not just that ``Tim is pink" has the form ``Fa." It's that ``Tim is pink" has the form ``Fa" and Tim looks like this: [insert visual experience here.]
* Sorensen, R. "Direct Reference and Vague Identity". Phil. Topics 28:1, Spr. 2000.
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