A decade and a half later, on the other hand, shares in Berlin Enterprises are holding up surprisingly well. Building: Letters 1960-1975, the third gargantuan volume in a seemingly inexhaustible fount of correspondence, is being enthusiastically reviewed. A second book, Isaac and Isaiah, by the historian David Caute, which covers Berlin's thorny dealings with the left-wing ideologue Isaac Deutscher, has just joined it on the Waterstones shelf. Most of the clever men of 1960s' Oxford, with whom Berlin wined, dined, caballed and zealously gossiped, are no more than footnotes, but, mysteriously, the man himself endures.
Or not so mysteriously. Building's blurb, trying to give some idea of what its subject was, or stood for, describes him as "a charismatic intellectual leader" as well as "a prominent thinker in his own right". Berlin, in other words, not only identified intellectual trends; he helped create them. He was, to use a job description that gets bandied about rather a lot these days, "a public intellectual". As a fellow of All Souls, Oxford and Chichele Professor of Social and Political Theory, his intellectual interests were bracingly diverse: the development of "liberal thought" (his real specialism), but also some of liberal thought's practical applications to, for example, the state of Israel, or – this being the height of the Cold War – the West's dealings with the Soviet bloc.
Berlin, it seems fair to say, was simultaneously the deediest kind of academic fixer and someone who believed that ivory towers had the seeds of their own destruction concealed in the foundation stones, that an academic was nothing unless he worked, however indirectly, for the public at large. Fifty years on from his globe-trotting heyday, the range of his contacts – John F Kennedy, the presidents of India and Israel, half a dozen British cabinet ministers – can seem as exhaustive as the stack of newspapers and magazines on which he regularly descended in an attempt to correct misinterpretations of what, even when laid out on the pages of The Sunday Times, were a set of highly complex intellectual positions.
Do "charismatic intellectual leaders" of the Berlin type still exist? Certainly the world is full of "public intellectuals" – the pages of the London Review of Books and Prospect positively swarm with them – but the charismatic intellectual leadership they offer nearly always has to be taken at its own valuation. This is not so much the fault of, let us say, Professors A C Grayling and Terry Eagleton, as a consequence of various changes in the nature of public debate which Messrs Grayling and Eagleton have to accommodate themselves if they want to be given a hearing.
One of them, of course, is that Berlin was sui generis. There never was anyone like him before, and there probably will not be anyone like him again. Another is the disappearance of several of the communication channels (Encounter, say, or The Listener) in which some kind of contact between the Berlins of this world and their prospective audience could be established. The most wide-reaching, alternatively, is the chasm that has opened up, here in the early 21st century, between what might be called the life of the mind and the life of the street.
To read half-a-dozen pages of Berlin's letters from the era of the Bay of Pigs and the Kennedy assassination is to be reminded of just how effectively a high-powered academic with a popularising taste could intervene on the wider cultural stage. If Berlin himself was having his lectures on the origins of Romanticism broadcast on Radio 4, then the Oxford historian A J P Taylor was contributing polemical articles to the Daily Express.
Berlin might have thought privately that Taylor, with whom he enjoyed chronically strained relations, was prostituting his talent, but the fact remains that Taylor, both through his newspaper articles and his off-the-cuff BBC lectures (delivered straight to camera, without notes) was a public figure known to millions who barely knew that Oxford academic history existed.
Naturally there are modern academics whose names and faces are known to the public at large, who write articles in the weekend press and appear on television to examine the sexual gymnastics of the Tudor court. Their difficulty, unlike Berlin, is the endless series of compromises forced upon them by the medium in which they operate. A popularising philosopher who turns up in the columns of a Sunday newspaper discussing the best way of living "the good life" usually ends up pitching his reflections slightly above the level of a cracker motto.
Richard Dawkins, to particularise, is an exceptionally clever man, but he is not, when he treks down from Olympus to the level plains of a literary festival, a public intellectual on Berlin lines, but simply the possessor of a solitary idea, and that, it might be argued, is not a very subtle one.
It would be wrong to suggest that the early 1960s were some kind of golden age of intellectual debate: their popular newspapers could be just as philistine as our own, and the wild halloo of the highbrow hunt just as rigorously enforced. And yet, with one or two laudable exceptions, the space in which intellectuals can discuss complicated issues in terms which the layman can understand gets smaller by the year. Berlin, on the evidence of his letters, was interested in pluralism, in liberal behaviour, "how to behave" in the broadest sense, in examining the social and political stand-offs of the kind that the modern world throws up and suggesting how the average liberal-minded citizen might respond to them.
He was, above all, a genuine – as opposed to a stage – liberal, who believed people were entitled to their beliefs and even to their prejudices, and both could be accommodated into a viable political fabric. Most of these concerns, you suspect, lie at the heart of what Matthew Arnold would have called the "regrettable modern tendencies" of our age, and it would be good for all – you, me, Mr Miliband and the next asylum-seeker jumping off the boat – if the forums existed in which they could be given some kind of airing.
