For months I’ve been thinking about writing a paper on the suddenly fashionable topic of _what vagueness is_. One of the most interesting views on the subject is by “Matti Eklund”:http://spot.colorado.edu/~eklundm/ivv.pdf who argues that a term is vague iff a tolerance principle is meaning-constitutive for it.
A tolerance principle is basically a Sorites premise. A tolerance principle is something like this, “Whereas large enough differences in F’s parameter of application sometimes matter to the justice with which it is applied, some small enough difference never thus matters.”
A principle is meaning-constitutive for a term if “if it is part of competence with it to be disposed to accept it.” (Both quotes are from Matti’s paper.)
I think that competence (in the sense of meaning the same thing as the rest of the linguistic community, which I think is the relevant sense of competence here) requires accepting very few principles, and certainly nothing as contentious as this. Note that Matti’s definition entails two other competence requirements, both of which I’ll argue against. First, being competent with vague term F requires knowing what F’s parameter of application is. Second, being competent with vague term F requires knowing that F is vague. Both of these might be plausible for _tall_ or _rich_, but they aren’t true, or even that plausible I think, for vague terms in general.
Consider the plausibly vague term _morally acceptable_. Imagine three speakers who have some thoughts about what is and isn’t morally acceptable. Tom thinks that an action is morally acceptable iff it is approved of by God. Jack thinks an action is morally acceptable iff produces more utils than any rival action would produce. And Mike thinks that an action is morally acceptable iff it’s an action a suitably virtuous person would perform.
It seems to me that Tom, Jack and Mike can all be competent users of the term _morally acceptable_. When they debate what things are morally acceptable, as they often do, they aren’t speaking past each other, rather they are genuinely contradicting what the others say. So they’re competent. But they don’t agree even on what kind of magnitude is measured by the term’s “parameter of application”. So the first competence principle is false.
As well as having very different views on what a tolerance principle for _morally acceptable_ should look like, they have very different views on whether such principles are prima facie plausible, let alone meaning-determining. Tom thinks no such principles are plausible, and certainly doesn’t think they are meaning-determining. Jack thinks that whether such principles are true turns on hard questions about the semantics and metaphysics of counterfactuals. But since he thinks hard questions about the semantics and metaphysics of counterfactuals don’t determine what’s meaning-determining for _morally acceptable_, these principles are not meaning-determining. Mike is more disposed to accept the prima facie plausibility of tolerance principles, though he too doesn’t think they are meaning-determining, since he thinks that if they were Jack and Tom would be conceptually confused (which he thinks they are not) rather than morally confused (which he thinks they are).
So I think Matti’s claim runs into trouble when we try to apply it to vague normative terms. But these are a _very large part_ of the class of vague terms.
UPDATE: Zoltan pointed out to me that Matti’s definition could be interpreted, and perhaps should be interpreted, as not requiring that competence requires knowing F’s parameter of application. Rather, it just requires being disposed to believe that whatever F’s parameter of application is, small changes in that parameter don’t change whether F applies. This seems to be correct, so one of my objections here fails. I still stand by the more general point that Tom, Jack and Mike can deploy the same concept while one believes it is vague and the other not, but my argument needs to be more careful here than I hinted at last night.
SECOND UPDATE: Matti responds at length in the comments. Be sure to read these as well.