It has sometimes been said of Isaiah Berlin that his aura and influence will dissipate once those who knew him cease proselytising for the cause. This has clearly not begun to happen, as can be seen, for instance, in the current excitement surrounding the centenary of his birth. This book is only one manifestation of a global celebration. But, one might respond, this represents merely the end of an era, a final conflagration that will be followed by a general recognition of the failure of Berlin's idiosyncratic liberalism, or indeed any kind of liberalism, to make sense of the new global situation. The Cold War is over, this argument runs, and we must thus leave Berlin and his ilk behind in a quest for new theories, capable of assimilating the variegated global practices of capitalism and terrorism. It is this judgement, perhaps more widespread in my native America than in Britain, that I hope to question here through an account of Berlin's influence on my decision to become, and my development as, a historian of ideas: an influence exercised entirely after his death.

The personal impression is a genre of which Berlin was an undisputed master. Perhaps it was, in the end, the only one in which he attained fluency. In saying this, I don't seek to question his brilliant and influential essays on Vico, Herder and others. Rather, I‘m claiming that Berlin at his best, even and especially in these scholarly essays, never strayed far from the personal impression. This was a consequence of his method. He never engaged in the self-effacing scholarship of his Cambridge School successors. Instead, he claimed that to interpret a text – that is, to interpret another human being's unique vision of life – requires us to call on the resources of our humanity first, and those of scholarship only second. Berlin was never excessively concerned with the concrete doctrines espoused by a thinker, or by contributions to the philosophical canon as such. Rather, he felt that his duty as a historian was to enter, as far as possible, into the sometimes alien and frightening value system of his subject. There is, then, a grain of truth in the claim that Berlin's influence will not outlast his personality. Indeed this criticism, paradoxically, grasps an important part of Berlin's project. But his personality did not die when his heart stopped beating. Rather, it survives in his texts.