features of British and American English largely agree but for a handful of divergences, for example: postvocalic ingliding and upgliding varieties of New England short coalescence of and variation of and in a few lexical items the vowel of poor, door, and sure variations in and Despite downplaying the divergences, Kurath argued that there is no "total pattern" (a term from ) that can be imposed on all English dialects, nor of even American ones: "The linguist must analyze the system of each dialect separately before he can know what systematic features are shared by all dialects, or by groups of dialects. He must distinguish between the systematic features and sporadic unsystematized features of each dialect, since every dialect has elements that are not built into the system. To regard unsystematized features as part of a 'system' and to impose an 'over-all pattern' are spurious notions that must be rejected. The description of a cognitively real polylectal grammar came with 's set of rules for the speech of Norwich that, presumably, could generate any possible output for a specific population of speakers and was psychologically real for such speakers such that native residents who normally exhibited sound mergers (e.g. between the vowels of days and daze) could accurately and consistently make the distinction if called upon to imitate older Norwich speakers. argues that comprehension across varieties, when it is found, isn't sufficient enough evidence for the claim that polylectal grammars are part of speakers' linguistic competence. argues that an extrapolated panlectal (or even broadly polylectal) grammar from "idiosyncratic" grammars, such as those found in , would still not be part of speakers' linguistic competence; argues that attempting a polylectal grammar that encodes for a large number of dialects becomes too bizarre and that the traditional reconstructed proto-language is more appropriate for the stated benefits of polylectal grammars. , notable for advocating the construction of polylectal grammars, says that the generative rules of such grammars should be panlectal in the sense that they are potentially learned in the acquisition process, though no speaker should be expected to learn all of them. Although question remains to their psychological reality, the usefulness of diaphonemes is shown in with the loss of the front rounded vowel phoneme in Greek words like ξύλο and κοιλιά; this vowel merged with in most words and in the rest, though the distribution varies with dialect. A diasystem would