The job of a descriptivist linguist

“Yes, there are rules of grammar. It is Coogan’s job (and yours) to try to obey them. And it is my job as a linguist to try and figure out what they are, and to state them precisely. And also to not be a jerk about it: my job as a language user is to forgive Coogan (or you) for any difficulty he (or you) might have in following them in spontaneous speech, and to use my common sense in trying to figure out what he (or you) might have meant.”