Essayist: Some linguists claim that competent speakers of a language have explicit knowledge of the rules of grammar for that language. However, linguistic ability is not the possession and utilization of a body of knowledge, or rules of grammar, but is more similar to a skill like riding a bicycle. Just as the typical cyclist does not need to know physics, neither does the language user need to know grammar rules.
Not everyone follows the same set of rules in acquiring a skill most accurately expresses a principle underlying the essayist's argument.