Although most students have more or less mastered the vagaries of English
spelling, few seem to be more than vaguely aware of the reasons for the
lack of correspondence between spelling and pronunciation in modern English,
and here it might be of interest to outline very briefly the historical
processes that produced the apparent chaos of the modern spelling system.
English is a Germanic language, and thus a close relative of modern Dutch, German, and the Scandinavian languages, and was brought to Britain in the fifth and sixth centuries A.D. by migrants from what are now southern Denmark, north-west Germany, and the Netherlands. The Anglo-Saxons, as these migrants are collectively known, were introduced to the Roman alphabet with the advent of Christianity in the late sixth century, as Latin was the language of the Church. This alphabet was quite carefully and consistently adapted to transcribe the sounds of English, and overall provided a fairly transparent representation of the pronunciation of the language into the eleventh century.
In 1066 England was invaded by the Normans, from north-west France. For the next two hundred years French largely replaced English as the language of administration and literature, resulting in the breakdown of the standard written language that had developed by the eleventh century, and when English started to be used again for these purposes from the thirteenth century, the spelling, while reflecting many of the changes in pronunciation that had developed during the intervening two centuries, tended to be irregular and inconsistent, due to the lack of a standard.
The scribes who copied manuscripts in this period (remember that printing had not yet been invented) were familiar with French, and they were much influenced by the spelling practices of that language and so introduced a number of letters new to English spelling, and also some new combinations of letters already in use. The result of this was in some points an increase in precision over earlier spelling, but in other points there was a significant increase in the number of ways in which a single sound could be spelt.
In 1476 the technique of printing was introduced into England by William Caxton, and the number of printing houses, mainly inside the London area, grew rapidly during the sixteenth century. Although the spelling in the early printed books tended to be inconsistent both within an individual text and among different printers, the printers came gradually to adopt a considerable degree of uniformity in the spelling, broadly based on the general usage of manuscripts produced in the London area in the second half of the fifteenth century and the first half of the sixteenth by professional scriveners, who had come to spell in a rather consistent, though still conservative and unphonetic, way.
It is unfortunate that such a system should have been adopted, because further major changes were taking place in pronunciation just at the time that the printing business was experiencing great growth. The uniformity of spelling in printed matter increased further during the seventeenth century, and by the end of that century the spelling system had, except in a very few points, been stabilised in its present-day form, all without significant response to the changes that had taken place in pronunciation during the previous two hundred years.
It should be clear from this brief sketch that the lack of correspondence between spelling and pronunciation that causes so much difficulty to both native and non-native learners of English has a very long history, and that the modern English spelling system represents, by and large, spelling practices of the fifteenth and sixteenth centuries, and the pronunciation of the fifteenth century and earlier.