Had Wittgenstein or Bertrand Russell ever tried to capture their ideal modern philosopher in fictional form, they might have called him something like David Crystal, and cast him as a hard-edged logician shut away in a world of exact proportions and determined right angles. The real David Crystal is a much warmer and more humane figure altogether; somewhat heroic, too, given the Augean task of compiling the forthcoming Cambridge Encyclopedia of the English Language.

It’s encouraging to find that most dedicated anatomist of the language is not interested merely in its minutiae, or in its philosophical superstructure, but precisely in those messier regions at the foot of the positivists’ tower. “I think if you were raised anywhere on the so-called ‘Celtic fringe’, you grew up with a heightened awareness of variation within the language.” Encouragingly, when I make a fist at remembering some lines by George Orwell, to the effect that once you start talking about the origins and function of words, you’re already talking about power relationships, he immediately and correctly identifies the sources as Orwell’s essays Politics and the English Language. It’s comforting that Crystal feels no unease at seeing those terms put together.

It’s equally comforting to detect down the telephone line from his home in Holyhead a subtle but definite regional twang, rather than the measured BBCOxford “Received Pronounciation” I had somehow expected from the author of Linguistics, a Pelican that sat in most student shelves of my generation. “It isn’t possible to live in Wales for five minutes without language issues being forced on you.” Crystal was born in Holyhead in 1941, and returned to his roots a decade ago, at another cusp in British educational life.

He’d studied at St Mary’s College, Liverpool, before going on to a BA at University College London, and then to what he calls (without a trace of irony) a “normal, happy academic life ” at the University College of North Wales, Bangor, where he’s now an honorary professorial fellow, and the University of Reading, where he taught for two decades and was professor from 1975 to 1985.

“Yes, until the cuts began to bite, I felt I was being turned from a teacher and researcher into a clerical officer. I applied for early retirement, didn’t get it, resigned anyway, and since then I’ve been what the Japanese call an independent researcher.” The Cambridge Encyclopedia, even in advanced proof state is a testimony to Crystal’s dedication, as well as his independence. If the first heaves of the Butler Act were detectable in the year of his birth, and if his 40th birthday was marked by the start of the biggest shift in educational policy since then - marked by the university cuts - the new book comes at an equally significant moment in the story, certainly as far as English teaching is concerned. “I feel we are at a watershed. It’s a very exciting time, and I’m very optimistic.”

Crystal’s sanguine but far from uncritical response to the national curriculum has everything to do with the emphasis it places on language awareness. “We’ve gone past that vague, waffly, 60s attitude of ‘let’s use language to the best effect’. I’m all in favour of not using terms without applications, but of course there’s a corollary to that, which is not to use applications without identifying terms at the same time. I imagine that when I come to revise this book” - as he’s currently revising the Cambridge Encyclopedia of Language - “it may not be as necessary as now to gloss most of the terms. By then, people, whether A-level students or more casual readers, may well have a more developed awareness of the technicalities.”

This leads us straight to the problem posed by Wittgenstein in Tractatus Logico-Philosophicus. Is it really possible to write about the language, when you only have the language to do it with? “That’s where the notion of metalanguage comes in, and that’s where there is a problem in educational terms, that of using terms which are not generally accessible, or which are no longer generally accessible, as they might have been when parsing and parts of speech were an integral aspect of English teaching. Despite my feeling that things are changing again, I’ve tried to avoid technicality in the Encyclopedia, at the expense of making it a much longer book.”

As well as being copiously illustrated, the book has an intriguing parallel development, with a consistent narrative and analytical progression balanced by boxed-off sub-chapters on more specific aspects of the subject at hand. “Each spread is designed to evoke three different responses, from the same reader as well as from different readers. One hopes there’s a reaction to the main text, something like ‘Ah yes, now I understand’; then to the smaller sections, along the lines of ‘Well, there’s something I didn’t know before’. I also hope that people will be amused and entertained by the word-games and anecdotes that complete the profile.”

Is Crystal conscious of working at a moment of maximum change in the language itself? “As with almost every other aspect of this, there’s no simple, single answer. Pronunciation isn’t changing any faster than it ever did. Grammar is only undergoing relatively slight change - an example would be dropping the article in sentences like ‘As teacher, he is doing a fine job’, where previously one would have said ‘As a teacher . . .’. It’s only when you come to vocabulary, the introduction of new words, that the rate of change seems to accelerate incredibly.”

What effects does this studying the language in a more technical context have on its use and reception? “Clearly, knowing what’s under the bonnet doesn’t in itself make you a better driver, but it makes you aware, and awareness is the first step to all sorts of things. In terms of language, it gives you a far greater receptivity to nuance, to why one form of words is being chosen over another. It can help identify misuse of language, by which I mean the misuse that goes on in propaganda, political language. Most crucially I think, it promotes tolerance, a greater sense of other people and their speech. That, again, is something that is promoted by living on the so-called fringes. Here in Holyhead, which is otherwise right in the heart of Welsh-speaking Wales, there’s a very interesting mix: about one-third Welsh, one-third English incomers, and one-third Irish. That’s very potent, and I think you do find, as I have going round schools, reading poetry and drama with children that in similar parts of the country, there’s a much greater understanding of and joy in regional variation.”

We agree that London, so often demonised as the great homogenizer, is actually wonderfully various in its linguistic and cultural mix. “Yes perhaps only in rural Hertfordshire or somewhere like that are you going to find a local variant unmixed in the way that people often like to imagine.” Nor are metropolitan institutions as guilty of, or as successful in, their cultural imperialism as more strident critics are inclined to say.

“I don’t think the BBC has any real impact on the language of the nation. It may institutionalise an aspect of the legacy, but not really beyond that. But, then, I can’t see that television is the great bogey that it’s painted. It offers children a tremendous sense and awareness of variations in language type, class, region, and so on.”

As to Received Pronunciation, the presumptive correctness of the ruling elite. “The truth is that RP is no longer spoken by any more than 3 per cent - I’d argued less, maybe 2 per cent - of the population. It still serves a function. Internationally, it’s perceived as the voice of Britian abroad (the BBC certainly has a role there) and it still waves a flag in places where there is a suspicion of American colonialism. There are probably more RP speakers in Moscow than in Britian. It’s been largely replaced by what is called Estuary English. You can even hear it in the speech of the young royals. The Queen will say “hoT”, whereas Prince Edward will say “ho’”, with that terminal glottal stop which is one of its central characteristics.”

Crystal shows no desire to rush to the barricades for RP, for regional accents, or for any other aspect of language, realistically aware that it is an area of cultural life that is not easily legislated for. “You can certainly form an Academy, which is what nations do when their pride is threatened by foreign invasion (France is the obvious example), or you can form pressure groups like the Queen’s English Society, but leaving aside that defensive capability, there really isn’t much you can do.” He’s equally even-handed when it comes to questions of gender-making in language (“predictably, the evidence points in opposite directions”) and on the issue of political correctness. “It isn’t the job of an encyclopedia to take sides. People might think that I’ve been fairer to PC than to other aspects. It’s a perfectly sensible idea that has to a degree been hi-jacked by extremists who have no real awareness of the issues. People who take the extreme view tend to forget that changing the name of something doesn’t change the reality.”

This is perhaps, his one reverse, for if the limits of our words indicate the limits of our several worlds, as Wittgenstein thought, then there remains the question of what came first, words or world. On this at least, Crystal prefers to remain silent. The language refracts, reflects and magnifies the lives lived within it. Only when that crystal is flawed or tampered with does it distort.

The Cambridge Encyclopedia of the English Language will be published on May 4 at Pounds 29.95.