The notion of linguistic competence as a cognitive system that produces knowledge not antecedently present in the mind of the subject, e.g., knowledge of grammatical relations in response to certain stimuli is an important contribution to philosophical understanding of linguistics, and of cognitive psychology in general. This notion has not been as well received as it should have been, in part because of certain false things that have been said about it. In particular, it has been said that a grammar of a language, conceived as a theory of linguistic competence, is an idealization, and that speakers know the rules of the correct grammar of their language. This paper shows that a theory of competence is not in any interesting sense an idealization, and that although a theory of linguistic competence, i.e. a grammar, aims at describing some real aspect of speakers, there is no reason to suppose that this is an aspect that would make it appropriate to say that speakers know the rules of the grammar
