August 20, 2006

Quantifier domain restriction and gel-filled bras

As Mark Liberman noted, security expert Bruce Schneier had some fun with this line from the Transportation Security Administration's byzantine list of prohibited carry-on items:

We encourage everyone to pack gel-filled bras in their checked baggage.

Schneier's riposte:

Everyone? Do I have to as well? Where should I go buy one?

But he wasn't the only online wag to crack this joke. Compare these two other iterations:

Everyone? First order of business, go buy a gel-filled bra. (Dvorak Uncensored)

Everyone means everyone. Even you. (Digg)

Nobody ridiculed the TSA for matching up an ostensibly singular quantifier (everyone) with an ostensibly plural personal pronoun (their). That sort of thing is old hat and hardly worth remarking upon (though Lord knows that doesn't stop us from remarking upon it, e.g., here, here, here, here, here, here, here, here...). The humor, such as it is, instead hinges on a supposed ambiguity in determining the domain of the quantifier everyone.

For the bloggers' joke to work, we have to toss out our Gricean maxims and apply an extremely uncooperative reading to the TSA's injunction. In a more explicit metalanguage, we could render the obviously intended proposition as:

For every person x such that x is traveling by air in the U.S. with gel-filled bras y, we encourage x to pack y in x's checked baggage.

The willfully obtuse interpretation given by the bloggers would go something like this:

For every person x such that x is traveling by air in the U.S., we encourage x to pack gel-filled bras y in x's checked baggage.

How do we know how to restrict the domain of a quantifier like everyone? We rely on a variety of contextual clues. In this case, since the sentence appears in a list of instructions for passengers, we know that everyone must at least be limited to the set of people traveling via U.S. airports, as even the disingenuous reading recognizes. Elsewhere in the TSA text, those domestic air travelers are given instructions through a series of law-like statements addressed to a generic you, e.g.,"You are permitted to bring solid cosmetics and personal hygiene items as such lipstick, lip balm and similar solids," or this bizarre bit of advice: "We also ask that you follow the guidelines above and try not to over-think these guidelines." (I tried not to over-think but failed. Sorry, TSA — over-thinking is de rigueur here at Language Log Plaza.)

In the ridiculed sentence, the TSA text shifts to a different type of indirect speech act. Instead of second-person address directed to a generic you, an "encouragement" is given to a generic everyone. But only a subset of passengers was meant to be selected by the use of everyone: those traveling with gel-filled bras, who must then decide where to pack them. The writer of the text could have made this shift of address more explicit by specifying the object of encouragement as "everyone traveling with gel-filled bras," but then that pesky coreference of everyone with their might have gotten in the way:

We encourage [everyone x] traveling with [gel-filled bras y] to pack [them y] in [their x] checked baggage.

The possible confusion between the two different coreferents of them and their would have been spared if the writer had chosen a singular pronoun her to match the antecedent everyone: "pack them in her checked baggage." But then the sudden change of addressee from all passengers to only female ones might have sounded a bit unusual. Of course, the non-gender-specific alternative his or her is no help here in avoiding the gender-bending ridicule of Schneier et al. In any case, I'm pretty sure the TSA wants to insulate itself from the tricky question of whether only women might be packing gel-filled bras. (This might explain why singular their was used in the first place.) It looks like the whole sentence would need to be recast in order to bypass all of these pitfalls.

The wisecrack at the TSA's expense actually strikes at the heart of a long-standing conundrum in the philosophy of language: how do we determine the intended domain of everyone and similar quantifiers? In the Anglo-American philosophical tradition, the question has been posed as a challenge to Bertrand Russell's theory of descriptions. Russell's theory is not well-equipped to deal with incomplete descriptions where quantifier domains must be inferred from pragmatic context. For more on the subject, see the April/June 2000 issue of Mind & Language, featuring "On Quantifier Domain Restriction" by Jason Stanley & Zoltán Gendler Szabó, with commentaries by Kent Bach and Stephen Neale. Some of the same ground is covered in a recent paper by Scott Soames, as discussed by Brit Bogaard on her blog Lemmings.

Posted by Benjamin Zimmer at August 20, 2006 12:10 PM