Sweet, (N. E. Gr., § 2202,/)) gives the following rule, "Such combinations as you and 1, we two, we three, we all take will instead of shall: We shall get there first, but / expect you and I wilt get there first. We two will be able to manage it quite well. I shall dream about those dogs to-night, I am sure I shall. So shall I. So we all will. Then he goes on to say, "If we put the all of the last example after the verb, the shall must be restored: So shall we all." Sweet does not account for the varied practice in the two last sentences, which, it will be admitted, is rather bewildering. It is not elucidated by what follows, "The explanation of this anomaly is that you and the other words added to we divert the attention frcrm the first person and make the idea of the second person prominent enough to suggest the more frequent will. It would be interesting to ascertain whether this last rule of Sweet's is borne out by the practice observed in Standard English. How far the discordant views of the two eminent grammarians are in harmony with commonly observed practice will beshownbelow(32).
25. The variety in the function of shall and will, and the way in which these functions are often blended, cause great difficulty as to the method of treatment. Most grammarians do not clearly distinguish between the three main functions of the verbs, with the result that the matter is left in a hopeless tangle, highly perplexing to the student. In this Grammar the words are discussed under three separate headings, according to the functions which come most prominently to the fore. This arrangement, although admittedly involving the making of some arbitrary distinctions, offers the advantage of enabling the student to form an outlined survey of the subject. In the following pages, accordingly, only those applications of shall and will are dealt with which exhibit futurity unmixed with other notions, or in which the tinge of futurity by other notions is so faint as to be practically negligible.
For detailed discussion of shall and will as volition-expressing verbs, and as modal verbs or auxiliaries, see, respectively, Ch. I of my Grammar of Late Modern English, and the treatise on Mood annexed to this paper.
26. The present use of we shall and will as auxiliaries of the future tense is said to be a compromise between historical and psychological principles. Enough has already been said of the historical principle which may have influenced the usage prevailing at the present day. Nor need the psychological principle occupy us long.