For the record, I have to agree with RiderOfGiraffes here. The idea that "Everyone doesn't X" is the same as "Not everyone does X" makes me deeply uncomfortable. As a writer, I strive to be precise in what I mean.
As Rider proposed earlier, some idioms are compressions of logical expressions, whereas some idioms are just mistakes that people have adopted. They're not the sole province of "foreign" countries like India, though. You can find these kinds of grammatically incorrect idioms in America too ("I ain't got nothing") and undoubtedly in England as well.
However widespread "I ain't got nothing" may be, though, it is still incorrect English. Children should be taught that it's not correct English. If everyone starts speaking such loose English, we'll lose the ability to communicate clearly with each other.
I think "Everyone doesn't X" falls into the same category of incorrect idioms that may be widespread, but should be stamped out at every opportunity, except in cases where they're used for humour. If someone said, seriously, "I ain't got nothing to hide,", I would regard them with the same discomfort as if they said "Everybody doesn't need to hide stuff". Both are unfortunate manglings that need to be discouraged where possible. HN seems as good a place as any to do so.
I don't at all disagree that the statement "Everyone doesn't X" is awkward-sounding. What I really object to is the assertion that "Everyone doesn't X" actually means "No one does X".
I would actually assume that someone using it in that way isn't a fluent speaker of (American) English, while using it as a reply to "Everyone does X" (perhaps with emphasis: "No, everyone doesn't X") seems like colloquial (American) English. I can't speak for Commonwealth English. :) When used that way, as a reply, it mirrors the original statement, which seems to me to have more impact than rephrasing the reply when disagreeing.
This is where formal mathematical (and programming) logic diverge from natural language. You are right to say that (mostly) "Everyone doesn't X" will (probably) be understood.
I, however, have 20 years experience in trying to teach mathematical logic and proof, and for those who use that style of expression there seem to be additional hurdles to overcome. They don't "get" why the logical converse of "For all X, Y" isn't "For all X, not Y". It's hard work convincing some of them, because it doesn't correspond to the language they use.
Similarly, in natural language people from different locations on occasion fail to understand each other.
I'm not trying to say that what one person says is right or wrong, I'm trying to point out the potential for misunderstanding, and the natural language analysis that corresponds to formal logic. Personally, I regard logic and proof as one of the intellectual highlights of human endeavor. The fact that natural language sometimes doesn't work that way needs to be understood.
That was (one of) my point(s).
I offer for consideration the difficulties that these issues create for natural language processing. If someone says "Everyone doesn't dance" - what exactly do they mean?
I understand the point you're making, and don't disagree that the literal meaning of the phrase is inconsistent with what people typically mean by it (much like "I could care less").
I offer for consideration the difficulties that these issues create for natural language processing. If someone says "Everyone doesn't dance" - what exactly do they mean?
If you want accurate reconstruction of the intended meaning, rather than wanting to constrain natural language to having a single meaning for each statement, then you'll need both contextual and general knowledge to figure out a meaning. I would say that it's clear that someone saying "Everyone doesn't dance", assuming that that was all that was said, meant "Not everyone dances", since it's rather obvious that some people do dance. If, however, they'd said "Everyone doesn't want to die", it would no longer be clear, since it's possible for people to believe that literally no one wants to die (with appropriate excuses made for suicides and posthumous heros). But I don't think that rules of English will be able to tell you anything more about the case than that it could be meant either way; outside information will have to guide the parsed meaning.
I just wanted to add something here in addition to my earlier comment ...
To me, with my background, the statement "Everyone doesn't X" means the following:
Everyone doesn't X.
It is the case that everyone does not X.
It is the case that every person does not X.
It is the case that for every person, they do not X.
Choose a person: they do not X.
No person does X.
If I want to negate the statement "Everyone does X", perhaps keeping as much of the original phrasing as possible for effect, then I would say:
No, not everyone does X.
Natural language is what it is, and I accept that to some people the appropriate negation is, in their idiom, expressed as "Everyone doesn't X." I'm just saying that my idiom should be accepted, just as yours should, and if you use that form, you will fail to communicate effectively with me.
I'm not claiming I'm right, or you're right, or anyone is right. Linguistics research accepts that we should allow each person their idioms. I'm saying that for effective communication, the differences should be understood and allowed for.
And I won't say any more on this topic. At least, for a while.
As Rider proposed earlier, some idioms are compressions of logical expressions, whereas some idioms are just mistakes that people have adopted. They're not the sole province of "foreign" countries like India, though. You can find these kinds of grammatically incorrect idioms in America too ("I ain't got nothing") and undoubtedly in England as well.
However widespread "I ain't got nothing" may be, though, it is still incorrect English. Children should be taught that it's not correct English. If everyone starts speaking such loose English, we'll lose the ability to communicate clearly with each other.
I think "Everyone doesn't X" falls into the same category of incorrect idioms that may be widespread, but should be stamped out at every opportunity, except in cases where they're used for humour. If someone said, seriously, "I ain't got nothing to hide,", I would regard them with the same discomfort as if they said "Everybody doesn't need to hide stuff". Both are unfortunate manglings that need to be discouraged where possible. HN seems as good a place as any to do so.