D. asks whether and to what extent presupposition, truth and grammaticality, and their interrelations, have any bearing on the Sapir-Whorf hypothesis. He claims that, as soon as one recognizes that deviance does not only depend on the 'universal mechanism' of grammaticality but on personal experience, the speaker's attitude etc. as well, the thesis of linguistic relativity becomes less refutable than transformational grammarians used to think.