Estimates, assertions and vagueness

I ask you to give me an estimate of how long a table is. You say "950 mm".

What did you do? You didn't assert that the table was 950 mm. Did you assert that you estimated the table at 950 mm? Maybe, but I think that's not quite right. After all, you might not have yourself estimated the table at 950 mm—you might have gone from your memory of what someone else said about it. So are you asserting that someone has estimated the table at 950 mm? No. For if someone had estimated the table at 700 mm and you could see that it wasn't (relevantly) near that, it wouldn't be very good for you to answer "700 mm", though it would be true that someone has estimated the table at 700 mm. Maybe you 're saying that the best estimate you know of is 950 mm. But that's not right either, because the best estimate you know of might be 950.1 mm.

Here is a suggestion. Giving an estimate is a speech act not reducible to the assertion of a proposition. It has its own norms, set by the context. The norm of assertion is truth (dogmatic claim): it is binary. But the norm of an estimate is not a binary yes/no norm as for assertion, but it can often be thought of as a continuous quality function. The quality function is defined by what it is that we are estimating and the context of estimation (purposes, etc.) Typically, the quality function is a Gaussian centered on the true value, with the Gaussian being wider when less precision is required. But it's not always a Gaussian. There are times when one has a lot more tolerance on one side of the value to be estimated—where it is important not to underestimate (say, the strain under which a bolt will be) but little harm in overestimating by a bit. In such cases, we will have an asymmetrical quality function. (This is also important for answering the puzzles here.) So in giving an estimate one engages in an act governed by a norm to give a higher quality result—but with a defeasibility: brevity can count against quality (so, you can say "950 mm" even if "950.1 mm" has slightly higher quality).

Moreover, what exactly is the quality function may depend on all sorts of features other than the exact value of the quantity being estimated. Thus, if you hand me a box with one cylindrical object in it and you ask me to give a good estimate of its diameter, how much precision is called for—i.e., how wide the Gaussian is—will depend on what the object is. If it is a gun cartridge, the Gaussian's width will be proportional to the tolerances on the relevant kind of gun; if it is an irregular hardwood dowel, the Gaussian's width will be significantly wider. So, in general, the quality function for an estimate that some quantity is x depends on:

• what quantity x is being given
• what the correct value is
• other properties of what is being estimated
• the linguistic context.

The second and third items can be subsumed as "the relevant bits of the extra-linguistic world".

So, here's a very abstract theory of estimates. Estimating is a language game one plays where the quality function keeps score. When one is asked for an estimate (or offers it of one's own accord), the context c sets up a function q_c from pairs <x,w> to values, and one's score in the game is q_c(x,@) where x is the value one gives and @ is the actual world.

Notice that this is general enough to encompass all sorts of other language games. For instance, the quantities need not be numbers. They might be propositions, names, etc. Assertion is a special case where the quantities are propositions, and q_c(x,w) is "acceptable" when x is true at w and is "unacceptable" otherwise. Or consider the game initiated by this request: "Give me any approximate upper bound for the number of people coming to the wedding." The quality function q_c(x,w) is non-decreasing in x: Because of the "any", saying "a googol" is just as good as saying "101", as long as both are actually upper bounds. Thus q_c(x,w) is "perfect" in any world w where no more than x people come to the wedding. In worlds w where more than x people come to the wedding, q_c(x,w) quickly drops off as x goes below the actual number of people coming to the wedding.

"Quantities" can be anything. They might be abstracta or they might be linguistic tokens. It doesn't matter for my purposes. Likewise, the values given out by the quality function could be numbers, utilities, or just labels like "perfect", "acceptable" and "unacceptable".

Conjecture: Assertoric use of sentences with vague predicates is not the assertion of a proposition but it is the offering of an estimate.

For instance, take as your quantities "yes" and "no", and suppose the context is where we're asked if Fred is bald. Then the quality function will be something like this: q_c("yes",w) is less in those worlds w where Fred has more hair, and q_c("no",w) is more in those worlds where Fred has less hair. Moreover, q_c("yes",w) is "perfect" in worlds where Fred has no hair.

What if I am not asked a question, but I just say "Fred is bald"? The same applies. My saying is not an assertion. It is, rather, the offering of an estimate. We can take the quantities to be binary—say, "Fred is bald" and "Fred is non-bald"—but the quality function is non-binary.

What about more logically complex things, like "If Fred is blond, he is bald"? Well, formally treat qualities as truth values in a multivalent logic, but in the semantics, don't think that they are in fact truth values. They are quality values. So, assign qualities to sentences (keeping a context fixed), using some natural rules like:

• q_c("a or b",w) = max(q_c("a",w),q_c("b",w))
• q_c("a and b",w) = min(q_c("a",w),q_c("b",w))
• q_c("~a",w) = "perfect" − q_c("a",w)

The rules may actually differ from context to context. That's fine, because this is not logic per se: this is the evaluation of quality (and that's how this approach differs from non-classical logic approaches to vagueness—maybe not formally, but in interpretation). Moreover, there may in some contexts be no assigned quality value to a particular sentence. Again, that's fine: there can be games with underdetermined rules.

In a nutshell: A vague sentence is an estimate of how the world is. Such sentences are not to be scored on their truth or falsity, but on the quality of the estimate.