No language in the world is homogeneous, or ever will be. Whereas earlier forms of English were characterised by extreme variation on all levels and Middle English is in fact best described as a loose conglomerate of unstable varieties, we usually lack any more detailed insight into what functions this variation had for the individual speaker. The social correlates so well known from modern sociolinguistics, such as age, sex, education, religion, can normally not be applied to the existing texts, nor can even the geographical range of recorded forms be determined with any degree of certainty. Finally, if modern dialect or other non-standard features are contrasted with (as the term non-standard implies) an accepted standard form of a language, this method would necessarily fail with Middle English even if we knew more about it than we do and, in view of the state of surviving documents, ever will. It is safe to assume that for its speakers the linguistic heterogeneity of Middle English was ordered in some way, but it was so only for continually shifting speech communities, whose number and individual geographical spread we know very little about. The scene changed dramatically in the fifteenth century: the emergence of a new standard language began to re-institute a linguistic norm for written supraregional English. This development was a natural consequence of the acceptance of English in public domains, and was speeded up by the change-over to English as the Chancery language in 1430.