(ii) It is necessary to clear the mind of the impression, derived from stereotyped written languages, that homogeneity and stability are natural states. Middle English texts represent a spoken language of many local varieties, all developing rapidly. So every linguistic fact should be thought of in terms of time, place, and circumstance, not because absolute precision in these points is attainable, but because the attempt to attain it helps to distinguish accurate knowledge from conclusions which are not free from doubt. If the word or form under investigation can be proved to belong to the author's original composition, exactness is often possible. In the present book, we know nearly enough the date of composition of extracts I, III, VIII, X, XI _a_, XII, XIII, XIV; the place of composition of I, III, X, XI _a_, XII, XIII, XVI, XVII (see map). But if, as commonly happens, a form cannot be proved to have stood in the original, endless difficulties arise. It will be necessary first to determine the date of the MS. copy. This is exactly known for _The Bruce_, and there are few Middle English MSS. which the palaeographer cannot date absolutely within a half-century, and probably within a generation. The place where the MS. copy was written is known nearly enough for IV _b_, _c_, XII, XIV _e_, XV _b_, _c_ (possibly Leominster), XVI, XVII; and ME. studies have still much to gain from a thorough inquiry into the provenance of MSS. Yet, when the extant copy is placed and dated, it remains to ask to what extent this MS. reproduces some lost intermediary of different date and provenance; how many such intermediaries there were between the author's original and our MS.; what each has contributed to the form of the surviving copy—questions usually unanswerable, the consideration of which will show the exceptional linguistic value of the _Ayenbyte_, where we have the author's own transcript exactly dated and localized, so that every word and form is good evidence. Failing such ideal conditions, it becomes necessary to limit doubt by segregating for special investigation the elements that belong to the original composition. Hence the importance of rimes, alliteration, and rhythm, which a copyist or reciter is least likely to alter without leaving a trace of his activities.