Boolean confusion

by Eszter Hargittai on May 1, 2005

This just came through on Drago Radev‘s IList:

I was visiting a government office recently and I noticed the following sign at the entrance:


I was tempted to walk in with a can of soda and absolutely no food on me but I eventually decided against it :)




henry 05.01.05 at 1:45 pm

not nearly as difficult a requirement to fill as in the hitchiker’s guide text adventure, where a particularly reticent door demanded you be in the possession of both tea *and* no tea at the same time to be allowed to pass.


Joel Turnipseed 05.01.05 at 3:54 pm

Well, let’s just be glad the post wasn’t a contradiction–who knows what you’d have been tempted to do?!


Joel Turnipseed 05.01.05 at 5:29 pm

[Meta: strange… henry, yer post appears before mine, though it came after: what does CT use for time stamp? Local machine?]


henry 05.01.05 at 6:31 pm

joel: possibly mine got held up in moderation? it’s pretty controversial ;)


jack lake 05.01.05 at 6:59 pm

Don’t be too harsh, they missed only one logic class.

For those of us who teach and can put this into an exam, you’ll be surprised at the number of graduate students who will do no better. (And will argue vehemently that they deserve the deducted points.)


Keith M Ellis 05.01.05 at 8:04 pm

Sorry, but:

A) Language isn’t logic; and,
B) Inclusive or is an acceptable construction in many languages/usages.


asg 05.01.05 at 8:48 pm

If the “or” in the sign were inclusive-or, it would mean that either no food, no drink, or both no food and no drink were acceptable. (That is, having one would not be required to get in.) The “problem” is that the sign said “or” when it presumably meant “and”.


Matt Austern 05.01.05 at 10:27 pm

When I was in high school, one of the colleges I applied to had the following question on their admissions form: “If you are female, are you of Swedish descent?”. I thought for a long time about how I should answer. (Yes, I know what they were trying to ask, but that’s not what the words said. A ‘yes’ answer would’ve been an opportunity to show that I was a smartass, which is arguably an advantage on a college admissions form.)


bi 05.02.05 at 1:39 am

Why do they care about Swedish descent only if you’re female? *scratch head*

And, this has nothing to do with boolean algebra, but I can’t resist: “TRESPASSERS WILL BE PERSECUTED”.


cs 05.02.05 at 7:35 am

bi – Maybe some rich alumn with a “thing” for young Sweedish women had endowed a scholarship.


Alex S. 05.02.05 at 9:40 am

It’s not a boolean choice, it’s a threat. If you bring food, you will not receive any drink. Obey, or go thirsty!


Hedley Lamarr 05.02.05 at 10:11 am

Just switch the OR for NOR!


Jeremy Osner 05.02.05 at 1:38 pm

The inarguable fact that “Language is not Logic” does nothing to make a sign that says “No food or no drinks” more idiomatic or sensible.


David 05.02.05 at 3:20 pm

boolean or type error? — an ad for some highend dogfood for sale at the local Petsmart contained the description “…varieties include lamb with rice and puppy….”


Keith M Ellis 05.02.05 at 11:20 pm

“The inarguable fact that ‘Language is not Logic’ does nothing to make a sign that says “No food or no drinks” more idiomatic or sensible.”

Why not? The sign is perfectly sensible. Only someone who attempts to parse the sentence as a mathematical statement will have trouble comprehending it. Everyone else who is a literate native English speaker will comprehend it as intended.

Smug put-downs of supposed misuse of language (like those on exhibit here) are the sophomoric equivalent of criticizing the innacuracy of Star Trek physics. In a deep sense, it’s a category error. I am beginning to believe that I could tolerate an analytic philosopher (of the linguistic philosopher subspeciality or inclination) who comes with substantial linguistics credentials. But the armchair variety? Not so much. Well, really, not at all.

Here’s something that will blow your minds: in natural language, double negatives are usually intensifiers and do not reduce to a positive. Wow! Isn’t that amazing?

Intellectual rigor is not essentially the metaphorical equivalent of a carefully wielded scalpel. It’s first and foremost the metaphorical equivalent of wielding the most appropriate tool.

I’d apologize for my ill-temper, but I expect better around these parts.


bi 05.03.05 at 7:04 am

No, no, no. We comprehend the message perfectly. It’s just that it still doesn’t look right. Much like the difference between “its” and “it’s”: if I wrote the previous sentence as “its just that…” I’m sure people will still know what I’m saying, but that doesn’t make it right.

I’ve not come across many natural languages where multiple negatives reduce to a single negative. Dialectal English maybe: “we don’t sell no beers to no bears.” And perhaps also Old English. But in Japanese, _shinakereba naranai_ (do-NEG-COND be-NEG) means “should”, and in Chinese — my native tongue — _bu4 ke3 bu4 cha2_ (not can not study) means “must be studied”. Oops.


Keith M Ellis 05.03.05 at 8:35 am

“…dialectal English…”

A language is the spoken language.


Belle Waring 05.03.05 at 8:39 am

here in my singapore condo we have painted signs that say “fire hardstanding area: not to be obstructed at all times.” I have long wondered if the claim that I was only obstructing it at *some* times would be a valid defence.


James Grimmelmann 05.03.05 at 9:10 am

“Or” is ambiguous in this context for another reason — it doesn’t specify whose option the choice is. One possibility is that it’s the reader’s choice, which means that the reader could walk in with soda but no food. The other is that it’s the writer’s choice, which means that if the reader walks in which soda but no food, the writer could point to the sign and say “sorry, no soda today, but you can bring in food.”

Either way, the reader can bring in one, but it makes a difference who gets to choose. (It’s the difference between additive conjunction and additive disjunction in linear logic.)


Brian Weatherson 05.03.05 at 1:41 pm

On a similar line to Belle’s example, I was completely confused the first time I rode the New Jersey Transit trains and heard the message “At the next station, all doors will not open”. I wondered why the train was stopping if all the doors would remain closed.


Tim 05.03.05 at 5:26 pm

A friend of mine was taking a psychological exam to determine his fitness for adopting a child. He is still puzzling over the acceptable answer to the following question:

True or False:
I rarely hear voices in my head.


Jeremy Osner 05.03.05 at 6:40 pm

A language is the spoken language.

In this case the relevant dialect is not “spoken English” (In which btw I think you would never ever hear the construction “no food or no drinks”), but rather “posted notice English”, the subset of the language that you see on signs. In this dialect there are two correct usages: “No food or drinks”, and “No food no drinks”. (This second may also be represented as “NO food drinks” where “NO” is twice the point size of the other words, and the other words are on two lines next to it.)

Another funny NJ sign: if you’re driving down rte. 9W from Nyack, when you hit Bergen County the sign says “Welcome to New Jersey/ Wipers on/ Lights on” — the first several times I saw it I thought it meant you had to keep your wipers and lights on at all times in the state.


lazyman 05.04.05 at 8:38 am

keith, I think that you’re letting your understanding of what such signs usually mean cloud your interpretation of what this one says; I don’t think anybody disputes the intent of the sign, they’re just struck by the strangeness of the construction used to express that intent.

Read on its own, it seems to present you with two options; of course that’s not what it’s meant to do, but that understanding is based on the (statistical) norm.

Of course, if you aren’t struck by its oddness at all, then your idiolect is, by my lights, pretty unusual.

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