If Ralph Miliband devoted his life to "the god that failed" — Marxism — Ernest Gellner devoted much of his to the god that didn't — Islam. But whereas Miliband's books were really political tracts masquerading as sociology, Gellner used the techniques of sociology to understand a genuine political problem: why Marxism had failed and Islam had flourished.
While Miliband saw his role as the subversion of the British State, Gellner was profoundly grateful to Britain and contemptuous of academics who indoctrinated students rather than opening their minds. In his first book, Words and Things, a sparkling demolition of the fashionable "linguistic philosophy" of the day, he denounced Oxford dons for sneering at ideas as "products of carelessness or confusion". In later life, he was equally scathing about those who corrupted academic life with political ideology.
Yet it was characteristic of Gellner that he remained on friendly terms with Miliband when they both taught at the LSE, despite Gellner's lifelong opposition to everything that Miliband stood for. Among the LSE's extraordinary array of émigrés and exiles in those years, Gellner distinguished himself above all as an observer of the intellectual life — a critical, even caustic observer, no doubt, but always rigorous in the pursuit of objective truth.
Where Miliband, following his master Marx, thought philosophers had missed the point, which was not to understand the world but to change it, Gellner realised that the world was changing anyway with terrifying rapidity and that understanding these changes was much more demanding than idle talk of revolution. To this end, he mastered the techniques, not only of philosophy, but of anthropology and sociology. Gellner's omnivorous intellectual appetite meant that he was equally at home among the "Saints of the Atlas" (the title of his classic study of the Muslim holy men of the Berber tribes of Morocco) and the "Narodniks of North Oxford" (his nickname for the tweedy targets of Words and Things).
Gellner was a product of Prague, the same German/Jewish/Czech melting pot as Kafka. At the end of his life he returned there to set up the Centre for the Study of Nationalism in response to ethnic cleansing in the Balkans. As one of the "disinherited minds" of the lost world of Habsburg Mitt-eleuropa, he never lost his acute ear for the sinister manoeuvres of intellectual charlatans. His excellent biographer John A. Hall (Ernest Gellner: An Intellectual Biography, Verso, £29.99) has unearthed Gellner's polemics against various fashionable figures of the day. He defended Bernard Lewis's critique of the self-hating Anglo-American liberal against Noam Chomsky, who blamed the West even for such communist monsters as Pol Pot, asking: "Why should a man judge his own society by an absurd standard, unless he has the need to use a standard which will then enable him to condemn that society with vehemence?"