Quote:
Originally Posted by mykwyner  A sentence like, "We ain't never done seen nothing like that there," is not ungrammatical because every native English speaker knows exactly what it means. |
Be careful of overgeneralisations. Many native speakers would have difficulty unravelling such a sentence (and you can count me in that group), although most would eventually arrive at the intended meaning -- this is, however,
despite the unorthodox grammar.
On the other hand, a sentence like "Post office, you please say me where is" would be considered ungrammatical in any English dialect, yet if a foreigner uttered this phrase to you, I'm certain you'd immediately understand the intended message.
I think your definition of "grammatical" is unhelpful, because actually it's very rare that anyone utters complete gibberish, unless they are suffering from certain forms of aphasia. The problem is that there are many, many different dialects of English (as there are of any language), and these dialects all have different grammar rules. Many sentences may be ungrammatical in some dialects but not in others.
For example, in most dialects of English, "do" is conjugated the same irrespective of whether it is used as a main verb ("I did my homework") or an auxiliary verb ("I did see the film"). However, in Cockney (and some other dialects), "do" is conjugated differently as a main verb ("I done my homework") and an auxiliary ("I did see the film").
When we as teachers say "This sentence is ungrammatical", that's really an abbreviation for "This sentence is considered ungrammatical by most speakers of Oxford English" (or "...General American" for American English).
Paradoxically, while grammar rules are (or should be) arrived at by observation and describe how native speakers actually use the language, we do need standards and conventions so that we can communicate meaningfully -- just as we find it convenient to have a "lingua franca" we can use to communicate to people on an international level.
Consider this: In some dialects of English, a double negative is used to emphasise the "negativity" of a sentence (as in: "I ain't got none"), while in others, a the second negative cancels out the first to make a positive (as in: "He can't not come", to mean that it would be impossible for him to stay away). Now, suppose you came across this sentence in a technical manual:
You shouldn't never supply hydrogen gas to this inlet.
Is the author saying that under no circumstances should hydrogen be supplied to this inlet, or that supplying hydrogen to this inlet is not completely inadvisable? Considering that hydrogen is a highly explosive gas when mixed with oxygen, this type of confusion could cost lives.
So here we have an example of a sentence which is grammatically correct in many dialects of English, but can be interpreted in two completely opposite ways.
To facilitate communication, then, we use an agreed standard, and as part of that standard we agree not to use double negatives at all. This is an artificial grammar, of course, arrived at pretty arbitrarily, but serves a purpose; and so this is what we normally teach in schools.
Of course, many native speakers who have had this standard grammar drummed into them are then inclined to view other dialects as somehow inferior or "incorrect", which, of course, simply isn't true. They're incorrect according to the prescriptive grammar rules agreed upon for the purposes of communication, but those prescriptive grammar rules don't apply to any variation of English except the artificial standards we've created ourselves.
The conflict is usually characterised as an intellectual war between "prescriptivists" and "descriptivists", which over-simplifies the whole issue greatly. Prescriptive grammar has its uses, but those uses do not include a Yorkshireman speaking to his mother, or a Kentucky farmer speaking to his sister. We prefer to teach students standard dialects on the grounds that standard dialects are pretty much universally understood and used in the mass media.