But what has this got to with language? This 2005 post on Language Log which I was alerted to by a tweet from Stan Carey of this excellent blog, makes a number of telling points about the debate between prescriptivists and descriptivists over what is "correct" English.
The normal model seems to be to say that a person is either one or the other. If you're a prescriptivist, you're telling other people how they should write and speak and telling them what's correct. If you're a descriptivist, you're happy to let it all hang out and just go with the flow...all change is good...whatever man...just allow it.
But that's a bit of a lazy caricature and it's probably better to see views distributed along a continuum line, where different shades of prescriptivism or descriptivism can be seen. For example, you might have very strong views on the use of the apostrophe in academic writing but be happy not to use it in your text messages or Facebook updates. That doesn't make you either a crazy hippy or a grammar nazi.
Geoff Pullum puts it more precisely than me - as he always does - when he talks about correctness conditions: the norms for your own language usage in your own variety of English:
If you typically say I ain't got no hammer to explain that you don't have a hammer, then the correctness conditions for your dialect probably include a condition classifying ain't as a negative auxiliary, and a condition specifying that indefinite noun phrases in negated clauses take negative determiners, and a condition specifying that the subject precedes the predicate, and so on.
He goes on to explain:
Descriptive linguists try to lay out a statement of what the conditions are for particular languages. And it is very important to note that the linguist can go wrong. A linguist can make a mistake in formulating correctness conditions. How would anyone know? Through a back and forth comparison between what the condition statements entail and what patterns are regularly observed in the use of the language by qualified speakers under conditions when they can be taken to be using their language without many errors (e.g., when they are sober, not too tired, not suffering from brain damage, have had a chance to review and edit what they said or wrote, etc.).
So, what linguists are not doing is just saying that whatever anyone says is right because they said it and therefore that's the way we talk. They're looking at specific situations and patterns and describing them grammatically. As Pullum goes on to say, sometimes people just make mistakes that, if they were to look back over, they'd probably choose to put in a clearer way. These could be features of grammar, punctuation, spelling or lexical choice. I'm sure many of us have looked back at things we've written and gone "Urgh". Linguists themselves might make mistakes by incorporating these errors into their sense of what the correctness conditions for a particular variety might be, so in turn build up an unrepresentative picture of that variety. So, as Pullum is at pains to point out, linguists can be wrong.
But equally, prescriptivists are often wrong (and more wrong!) when they claim that such-and-such a structure (a conjunction at the start of a sentence, preposition at the end, double negative etc.) is always wrong just because them's the rules.
So, to cut a long story short, the debate between what's correct or incorrect is actually much more to with context than it is to do with hard and fast rules. And for A level English Language, which is what this comes back to, finding a more nuanced position between the extremes of labelling a language commentator as either prescriptive or descriptive, is likely to get you a lot of credit in the ENGA3 exam. While it's not for everybody, this sort of discussion could be the difference between a top B and an A grade, or even that elusive A*.