Glen on legalistic reading and Venn diagram problems

In an earlier post, I asked why the sentence "Thirty students take geometry, and 25 students take Spanish" seems, to me, an acceptable -- and typical -- way of saying: "Thirty students take geometry, and another set of 25 students take Spanish."

I think Glen has explains it:

Out of context, there is an implicit contrast: "Two students do X, and three students do Y" is a common sentence pattern in English, which implies that you are talking about five students and how they divide up. If X and Y aren't obviously alternatives, this form implies that they are. "Two students take Spanish and three take French" would be natural English if talking about five students. If talking about four students, it would be odd. "Two students take Chinese, and three students are hispanic" might prompt an exasperated, "What, hispanic students can't take Chinese?", because it does seem to contrast X, taking Chinese, with Y, being hispanic.

If you didn't mean to contrast one group of students from another, you would probably say it differently. For example, "The geometry class has 30 students, the Spanish class has 25, and some students could be in both classes."

But in the context of a math problem, all of that changes. Math problems written in natural language still require you to make disambiguating assumptions--it is still natural language, after all--but they want to you put more weight on what is literally said and less on other factors ("bayesian priors").

In such a context, you are trained to interpret "Two students do X, and three students do Y," without assuming two disjoint groups. You learn to be literal and legalistic in a math problem context, which is a context-based re-weighting of the factors involved in interpretation of language.

I'm glad Glen has used the term "legalistic": that's exactly what I was thinking.

I'm not a legal reader by any means, but when I do read legal documents -- or, more to the point, when I read a legally vetted explanation of a state of affairs to which I object -- I instantly switch to a literal-minded, 'legalistic' mode. I take it as a given that legally vetted statements count on readers to make inferences that aren't in fact true, and to be mollified by those inferences to boot.

In short, legally vetted public relations statements, which is what I'm talking about, practice a particular form of lying by omission, which is lying via exploitation of the conventions of natural language. (I'll have to be on the look-out for examples...)


Further:

I have an email from Katharine asking whether I'm thinking of the Gricean maxims (pdf file). I hadn't been, because I'd never heard of the Gricean maxims, but I think she's right.

question for Katharine

I've been meaning to post something about the wording of Venn diagram problems for a while now.^*

e.g.:

Thirty students take geometry, and 25 students take Spanish.

I have finally begun to divine fairy rapidly that what this sentence really means is: 

Thirty students take geometry, and 25 students take Spanish. Of those students, some may take both geometry and Spanish. Then again, maybe not.

I divine it, but I don't like it. I would never, ever write the first sentence if what I meant was the second sentence(s). (So no one's going to hire me to write Venn diagram problems any time soon, but never mind.)

I've called this post "question for Katharine" because I'm pretty sure that, as a writer, I'm following an implicit rule I know but can't name.

I might write the first sentence if I meant:

Thirty students took geometry, and another 25 students took Spanish.

Actually, I probably would write the more explicit two-sentence passage because I specialize in spelling things out. But I wouldn't think it was wrong if someone else wrote Thirty students take geometry, and 25 students take Spanish when what they meant was Thirty students take geometry, and another 25 students take Spanish.

But I perceive Thirty students take geometry, and 25 students take Spanish as an incorrect way to express Thirty students take geometry, and 25 students take Spanish. Of those students, some may take both geometry and Spanish. Then again, maybe not.

In short, according to my non-conscious rulebook: 

Thirty students take geometry, and 25 students take Spanish ≅
Thirty students took geometry, and another 25 students took Spanish.

but

Thirty students take geometry, and 25 students take Spanish ≠
Thirty students take geometry, and 25 students take Spanish. Of those students, some may take both geometry and Spanish. Then again, maybe not. 

Why is that?

I started to think it through the other day, but then it struck me that Katharine, who is a linguist, may already know.



^* awhile? a while? I'm going to figure that out soon.