Thus, there are people who “prescribe” to police this. Dictionaries were created as policing tools. There are also linguists who “describe”. Most linguists, unlike the LLog scholars, are content with this idea. However, the process differs from a discussion of dialect. For one thing, a discussion of dialect is not usually held in dialect, and is not an example of what it attempts to describe. Local dialect is not used for intra-communal communication, and thus nobody wishes to studiously internalize the norms that are described, in opposition to standard. You will not find people using the word “wrong” about common dialect phrases, as Liberman has about standard, when a phrase in dialect is proven to be in common use. The norms of the local dialect are not well known to the speakers, they are intuitive, and thus people do not discuss them very much. The dialect is not usually written down. I could go on.

The difference is crucial, and yet linguists often maintain that the standard dialect is just one more dialect. In sociolinguistic terms, that is utterly wrong.

I’m afraid the existence of a standard language is all very mixed up with oppressive power, and this is why linguistics does not deal with it very well. Standards do ultimately derive, to some degree, from precedents set by powerful figures, groups, classes or organizations, and it must be the case even to some extent in a non-literate society. An extremely powerful leader, such as a Mao, can wave his hand and alter usage. An influential writer can move things a little. The discussion that led us here was a very important day in the life of “The reality….”. That discussion will come up 1st on Google, perhaps, and the big chief says no, and that one million customers can be wrong. How many people need to use the phrase before we call it “right”? Can there be a scientific answer?

And, I would say that an important difference between prescriptivism of the type derided on LL and whatever formal linguists do when they limit the scope of their inquiry is that the latter make a clear distinction between “standard” and “correct,” as I’m sure you’re aware. The prescriptivists most criticized (and such people do seem to exist) see one context of communication as setting the standard for all contexts, leading to people who demand of their drinking buddies that they follow the style guide of XYZ publication (in the extreme case).

This line between standard and non-standard is too often glossed over. Imagine a grammar of English that made only statements that were true of every single dialect of English. A thin book? That is not the book that Pullum wrote for CUP. And finding this important line is not easy at all, corpus linguistics notwithstanding.

As to the final paragraph, yes, very akin to prescriptivism. Especially if you are the first person to describe a language, and others will use your work as a later reference. And in that case you may wish to create prescriptive standards in order to aid communication.