If Berlin too often disparaged his principal rivals in the field of political philosophy, he persisted in conceiving himself as the sole significant practitioner of intellectual history in this country long after that self-characterisation had ceased to be credible. Writing to Jean Floud in January 1996, he insisted that: “In Germany there are chairs in Geistesgeschichte, Ideengeschichte etc. In Italy also, in America too. In England — two minor posts, occupied by pretty inferior people.” At the time, Quentin Skinner was still Professor of the History of Political Thought in Cambridge. John Burrow had just been appointed Professor of European Thought at Oxford: some “minor posts”, some “inferior people”. One might go on.

But that would be to miss the point. For what finally emerges from these pages is not so much the man as a thinker. Several thousand pages later, Berlin himself remains a shadowy figure. Of the ordinary stuff of his life — his loves and travels, of places and peoples seen, of reactions to landscape and scenery — we learn conspicuously little. Perhaps he preferred it that way. Perhaps too there are parallels to be drawn between the curiously underdeveloped subject of these letters and the disturbingly two-dimensional eloges to friends recently passed that litter its later volumes.

Of Berlin’s profounder thoughts, more precisely of the genesis of his political ideas, there is altogether more to be savoured here. That is possibly as it should be. Berlin believed that all major thinkers were inspired by one, often quite simple, vision: their way of looking at things. However complex its subsequent expression, this insight remained, in principle, accessible. The primary purpose of interpretation was to expose it. Berlin has not been without able readers since his death. But no one essayed that task more thoroughly than himself. This is where he made that attempt.

The basis of Berlin’s thought, the root of all his reactions to the world, and the foundation of all his political prognostications for the world, lay in his sense of Jewishness. This point cannot be emphasised too strongly since, when pushed, he denied it. These Letters furnish chapter and verse to prove that he protested too strongly on that occasion. There neither was, nor is, anything in the least discreditable about this. The fact remains — it is impossible to read these letters through without concluding — Berlin defined himself as a Jew before everything else, before being a “Russian”, before being an Englishman, before being a philosopher too.

There was nothing specifically religious about this attachment. Berlin declined to describe himself either as an atheist or an agnostic. But this was only because the concept of God held “no meaning” for him. That said, he acknowledged the possibility of “religious feelings” and regarded those of his friends, notably Freddie Ayer and (more subtly) Hugh Trevor-Roper, who did not, as in some sense deficient — anyway, as thereby “incapable . . . of understanding what men live by”. It is difficult to disagree.

Brought up Conservative (“not, strictly speaking, Orthodox”), he remained an occasionally observant Jew all his life. This was, in part, owed to his distinguished lineage and, in part out of deference to his parents. It was more because he naturally “identified . . . with the Jewish community”. He “liked . . . to feel a member of a community that (had) existed for three thousand years”. This involved a certain complicité — that invariably irrational, possibly even unjustified but nonetheless ineradicable sense of similarity, comparable to the affinity that Tocqueville always acknowledged among fellow French aristocrats. It also involved something else. This was the sense, beyond mere affinity, of real and exacting loyalty: in other words, the proper demands of irreducible commitment.