Logic in the Times

by Brian on January 13, 2004

From the NY Times:

Tim Hurd, a spokesman for the National Highway Traffic Safety Administration, a branch of the Transportation Department, said a vehicle either met the specific technical requirements of being a light truck, or it did not.



robin green 01.13.04 at 5:10 am

This, though, is not a tautology, because it purports to give us a new piece of information: namely, that the technical requirements for light trucks are completely unambiguous. A tautology, by contrast, does not convey any information in the strict sense. (However, as any mathematician knows, a complex mathematical tautology may still tell somebody something they didn’t know already, thus demonstrating that the concept of “learning something new” or “new information” isn’t as simple as it looks, either.)

So, even though the sentence from the Times looks like a simple sentence in classical logic, it really isn’t classical, because it admits the possibility of ambiguity, and therefore is non-classical.

Ha! Take that!


Brian Weatherson 01.13.04 at 5:35 am

This is assuming that classical logic takes a nap when sentences are ambiguous. That isn’t something I’d be prepared to admit, and a lot of other philosophers would agree.

I do agree, however, that the sentence communicates something non-trivial. Just what that is is a little unclear. Mr Hurd wanted to communicate that the standards are completely objective, which is obviously different from being unambiguous. It’s a really interesting research project to figure out just how claims like that could get to be the speaker-meaning of tautologies like Mr Hurd uttered. Any suggestions are more than welcome!


dsquared 01.13.04 at 1:55 pm

Raises the interesting prospect of some items which are not vehicles being both light trucks and not light trucks.

Does the set of all and only all light trucks meet the technical criteria for being a light truck?


Brian Weatherson 01.13.04 at 2:27 pm

Hmm, looking through the article it seems that an elephant might satisfy the sufficient conditions for being a light truck (especially ground clearance, which seems to play an important role in this case) but not the necessary conditions (especially being a truck). So maybe according to the rules it is both a light truck and not a light truck.


Matt Weiner 01.13.04 at 10:33 pm

What happens if you replace “ambiguous” with “vague” in Robin’s comment? I think what’s being communicated is that the standards are determinate. (I also think this may be what Robin meant; the senses philosophy has assigned to these words aren’t necessarily the one’s non-philosophers use, if Robin indeed is a non-philosopher.)


Brian Weatherson 01.13.04 at 11:14 pm

If you replace “ambiguous” with “vague” you get something close to a thesis I defend here – that the speaker meaning of “p or not p” can quite easily be “Determinately p or determinately not p”. Many people think that’s the truth condition of “p or not p”, but they’re wrong. [About here I’d like to insert a 50 page argument to that effect, but it’s late and the server might crash.] But I’d basically agree that’s what Hurd might have meant, even if I disagree that’s what his words mean.

What surprised me a little was the fact that when Hurd clarified what he’d meant, he didn’t stress the lack of vagueness, but the lack of subjectivity. There are no judgment calls involved in classifying something as a light truck or not. I guess there’s a connection here – after all judgment calls more or less entail vagueness – but it wasn’t exactly the meaning I expected.

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