Trevelyan's "ENGLISH SOCIAL HISTORY" (Penguin 2000 reprint) offers the following enlightening passage about Caxton's role in the formalization of the English language. It's worth the struggle to read! The relevant text is highlighted in bold.
..... He began by translating French books into English. While so engaged, he fell in with the new mystery of printing with movable types, and studied it at Bruges and Cologne. In 1474-5 he produced abroad two of his own translations (one of them a medieval romance and the other The Game and Playe of Chesse), the first books to be printed in our language.
Then in 1477 he brought over his press to England, set it up at Westminster, under the shadow of the abbey, and there, during the remaining fourteen years of his life, under royal and noble patronage, he poured out nearly a hundred books, many of them in folio, and most in the English tongue. Among them were Chaucer, Gower, Lydgate, Malory's Morte d'Arthur and translations of Cicero and of Aesop's Fables. His industry was prodigious. Besides his constant and arduous labours at the press he translated as many as twenty books. He had indeed a missionary zeal for the dissemination of good and useful books among his countrymen 'in our English language'. His diligence and success as translator, printer, and publisher did much to lay the foundations of literary English, and to prepare the way for the great triumphs of our language in the following century.
His own use of the machine which he established as part of our island life was at once ideal and practical, but it was not controversial. Yet the press would henceforth be the weapon of every political or religious controversy; the tempo of the spread of ideas and of knowledge would be immensely accelerated. But in the year Caxton died that consequence had scarcely yet been realized.
On the other hand, Caxton was well aware of the importance of his work in fixing the form of the English language for educated people, and he therefore gave much thought and asked much advice as to the dialect into which he had best translate the books he printed. He described these difficulties in his Prologue to the Eneydos, his translation from a French paraphrase of Virgil's Aeneid:
After dyuerse werkes made translated and achieued, hauing noo werke in hande, I, sittyng in my studye where as laye many dyuerse paunflettis and bookys, happened that to my hande came a lytyl booke in frenshe, whiche late was translated oute of latyn by some noble clerke of fraunce, whiche booke is named Eneydos made in latyn by that noble poete and grete clerke Vyrgyle.
And whan I had aduysed me in this sayd boke, I delybered and concluded to translate it in-to englysshe. And forthwyth toke a penne and ynke, and wrote a leefe or tweyne whyche I ouersawe agayn to corecte it. And whan I sawe the fayr and straunge termes therin, I doubted that it sholde not please some gentylmen whiche late blamed me, sayeng that in my translacyons I had ouer curyous termes whiche coude not be vnderstande of comyn peple and desired me to vse olde and homely termes in my translacyons. And fayn wolde I satisfye euery man; and so to doo, toke an olde boke and redde therein and certaynly the englysshe was so rude and brood that I coude not wele understand it.... And certaynly our language now vsed varyeth ferre from that whiche was vsed and spoken when I was borne.... And that comyn englysshe that is spoken in one shyre varyeth from another. In so moche that in my dayes happened that certayn marchauntes were in a shippe in Tamyse, for to haue sayled ouer the see into Selande, and for lacke of wynde thei taryed atte Forlond [North Foreland in Kent], and wente to lande for to refreshe them; And one of theym named Sheffelde, a mercer, cam in-to an hows and axed for mete ; and specyally he axyed after eggys ; and the goode wyf answerde, that she coude speke no frenshe. And the marchaunt was angry, for he also coude speke no frenshe, but wolde haue hadde 'egges' and she vunderstode hym not. And theene at laste another sayd that he wolde haue 'eyren' then the good wyf sayd that she vnderstod hym wel. Loo, what sholde a man in thyse dayes now wryte, 'egges' or `eyren'?
Certainly it is harde to playse euery man by cause of dyuersite and chaunge of langage. And som honest and grete clerkes haue ben wyth me, and desired me to wryte the moste curyous termes that I coulde fynde. And thus between playn, rude and curyous, I stand abasshed, but in my judgemente the comyn termes that be dayli vsed, ben lyghter to be vnderstonde than the olde and auncyent englysshe. And for as moche as this present Booke is not for a rude vplondyssh man to laboure therein ne rede it, but onely for a clerke and a noble gentylman that feleth and vnderstondeth in faytes of armes, in loue, and in noble chyualrye, therefor in a meane bytwene bothe I haue reduced and translated this sayd booke in to our englysshe, not ouer rude ne curyous, but in suche termes as shall be vnderstanden, by goddys grace, accordynge to my copye.
We thus see that Caxton had a choice to make. He had no dictionaries to cramp or to guide him. As he sat in his book-littered study considering the matter, he had not, as we have and as even Shakespeare had, an English language 'given' whose limits he might extend but whose framework he must accept. The number of dialects were almost as numerous as the counties of England, and moreover they were perpetually changing. The northerner, the west country man, even the housewife of Kent with her 'eyren', could not easily understand either the London merchant or one another. The victory of the speech of London and the Court may perhaps have been ultimately inevitable, but it was rendered certain and rapid first by Chaucer and his fifteenth-century imitators, who drove the west-midland dialect of Piers Plowman out of the field among the educated classes; then by the products of Caxton's press; and last and most of all by the English Bible and Prayer Book, which in Tudor times, thanks to the printing press, reached everyone who could read and many who could only listen. Thus, in the course of the fifteenth and sixteenth centuries, the educated English obtained a common dialect, corresponding to 'literary English'; and, as education spread, this dialect became the language of all the land.
Throughout the troubled reigns of the Lancastrian and Yorkist kings, London remained peaceful and her wealth constantly increased : the pomp and parade of her magistrates on solemn occasions grew ever more imposing in the streets and on the river; her civic, ecclesiastical, and domestic architecture grew more rich and beautiful, till no wonder at the end of the century the Scottish poet Dunbar exclaimed : 'London, thou art the flower of cities all!'
The government of London during this period was conducted, not by the democracy of manufacturing crafts but by members of the great merchant companies. The Mercers, Grocers, Drapers, and to a lesser extent the Fishmongers and the Goldsmiths, supplied nearly all the mayors and aldermen of fifteenth-century London. The members of these great companies, whatever their names might portend, were not in fact confined to the business of mercers, drapers, and so forth their chief profits came from the export overseas of all kinds of goods, principally of corn, wool, and cloth. They had their houses and their agents, like William Caxton, established in Bruges and other great trading cities of Europe. They owned plenty of good English ships, not only in London but in other ports, and traded also in hired foreign bottoms. But the merchants of Italy and of the north German Hanse still brought their own goods in their own ships to London. The wharves, crowded with vessels of many nations, stretched down the river from the Bridge, battlemented with tall houses and decorated with ever fresh supplies of traitors' heads, to the royal palace and armoury at the Tower.
The merchant aristocracy that ruled the capital wisely resisted the temptation to take an active part in the struggle of the rival families for the Crown (it was only in Stuart times that London was in a position to make and unmake kings). But they compelled the armies of the Red and White Roses to respect London's liberties and commerce, and each successive government, whether of Henry VI, Edward IV, Richard III, or Henry VII, regarded the friendship of her merchants as 'indispensable to the solvency of the national exchequer. Edward IV courted their friendship in personal and domestic visits to the City, almost beneath the dignity of a king. The Staplers continued to lend money to government. The wool off the royal estates, and off the land of political magnates like Lord Hastings and the Earl of Essex, was sold abroad through the good offices of London merchants. Gentry like the Stonors, owning West Country sheep runs, were proud to be styled Merchants of the Staple. The 'landed and monied interests' were often indistinguishable, even at this early date. Wealth acquired in trade already flowed into and fertilized the land.
1. In the reign of Henry VII an Italian traveller wrote: 'in one single street, named Strada, leading to St Paul's, there are fifty-two goldsmiths' shops, so rich and full of silver vessels, great and small, that in all the shops in Milan, Rome, Venice and Florence put together, I do not think there would be found so many of the magnificence that are to be seen in London' (Italian relation of England, Camden Society, 1847, p. 42). Strada is probably not the Strand, but Cheapside: see Miss J. Davis's article in History, April 1932.