"Linguistics Class" What is the discussion mainly about?

Narrator: Listen to part of a discussion in a linguistics class.
Professor: What comes to mind when I say the word grammar?.
Student 1: That’s easy. English class and lots of rules.
Student 2: Memorizing parts of speech... like nouns and verbs.
Student 3: Diagramming sentences.
Professor:
Well, yes, that’s fairly typical. But today we’re going to look at grammar from the point of view of the  Q12
linguist, and to do that, we really have to consider three d stinct grammars for every language.
   The first grammar is referred to as a mental grammar. And that’s what a speaker of a language
knows, often implicitly, about the grammar of that language. This has also been called linguistic
competence and from that term competence grammar has become popular. I like to think of it, of mental or
competence grammar, I mean... I like to think of it as an incredibly complex system that allows a
speaker to produce language that other speakers can understand. It includes the sounds, the
vocabulary; the order of words in sentences and... even the appropriateness of a topic or a word in a
particular social situation. And what’s so amazing is that most of us carry this knowledge around in our heads
and use it without much reflection.
   One way to clarify mental or competence grammar is to ask a friend a question about a sentence.  Q13
Your friend probably won’t know why it’s correct, but that friend will know if it’s correct. So one of the
features of mental or competence grammar is this incredible sense of correctness and the ability to hear
something that "sounds odd" in a language. Haven’t you had the experience of hearing a sentence,and
it stood out to yoU?It just wasn’t quite right?For native speakers we can call this ability native intuition,
but even language learners who’ve achieved a high level of competence in a second language will be
able to give similar intuitive responses even if they can’t explain the rules. So that’s mental grammar or
competence grammar.
   Okay then, that brings us to the second type of grammar, and this is what linguists are most
concerned about. This is descriptive grammar, which is a description of what the speakers know intuitively
about a language. Linguists try to discover the underlying rules of mental or competence grammar and
describe them objectively. So descriptive grammar is a model of competence grammar, and as such, it
has to be based on the best effort of a linguist, and consequently, subject to criticism and even
disagreement from other linguists. Because no matter how skilled a linguist is, describing grammar is an
enormous task. In the first place, the knowledge is incredibly vast and complex; inthe second place the
language itself is changing even while it’s being described; and finally,the same data can be organized  Q14
in different but equally correct ways in order to arrive at generalizations. And the ultimate goal of a
descriptive grammar is to formulate generalizations about a language that accurately reflect the mental
rules that speakers have in their heads.
   But, getting back to what most people think of as grammar—the grammar that we may have learned
in school. That’s very different from either competence grammar or descriptive grammar because the
rules aren’t meant to describe language at all. They’re meant to prescribe and judge language as good
or bad. And this kind of grammar is called, not surprisingly, prescriptive grammar because of its
judgmental perspective. Again, to contrast prescriptive grammar with descriptive grammar, just think of
descriptive generalizations as accepting the language that a speaker uses in an effort to describe it and
recognizing that there may be several dialects that are used by various groups of speakers and that any
one speaker will probably choose to use different language depending on the formality, for example, of
the situation. On the other hand, prescriptive rules are rigid and subject to enforcement. Prescriptivists want to make all speakers conform to one standard in all situations, and that tends to be a very formal
level of language all the time.
   Now which of these types of grammar do you think you were learning in school when you had to
memorize parts of speech and rules and diagram sentences?
Student 2: Sounds like prescriptive grammar to me.
Professor:
Precisely. But how did prescriptive rues get to be accepted, at least in the schools? And probably even
more important, why are so many of these rules disregarded even by well-educated speakers in normal
situations?
Student 1: Did you say disregarded?   Q15
Professor:
I did. Some of you may recall that during the seventeenth and eighteenth centuries in Europe, Latin was
considered the perfect language and was used by the educated classes. The argument for the  Q16
perfection of Latin was reinforced by the fact that Latin had become a written language and, consequently...
Latin had stopped changing in the normal ways that spoken languages do, so the rules were also fixed,
and for many writers of English during that period, the rules of Latin were held as a standard for all
languages, including English. But the problem was that English had a different origin and very different
constructions. For example, hoW many times have you heard the prescriptive rule, "never end a  Q17
sentence with a prepositien?" This is a Latin rule, but it doesn’t apply to English, se it sounds very formal
and even strange when this Latin rule is enforced. Now, how many of you would say, "What are we
waiting for?" I think most of us would prefer it to "For what are we waiting?" But as you see, this breaks the
rule—the Latin rule, that is.
Student 2:
So we’re really learning Latin rules in English classes. No wonder 1 was confused. But wouldn’t you
think that.., well, that things would change? I mean, Latin hasn’t been recognized as a world language
for a long time.
Professor:
You’re right. But the reason that prescriptive rules survive is the school system. Teachers promote the
prescriptive grammar as the standard for the school, and consequently for the educated class. And
"good" language is a requisite for social mobility, even when it’s very dissimilar to the mental grammar
or the descriptive grammar of a language.