It is a great honour to have been invited by the Association for the Study of Ethnicity and Nationalism to give this Ernest Gellner lecture. Ernest Gellner was for some years a colleague here at LSE, but he had been an intellectual hero of mine ever since, in the midst of an undergraduate philosophy course in the mid-1960s, I read Words and Things. His contribution, in substance as in style, was unique. He did not put up with cant, he was provocative in judgement, transgressive in regard to disciplinary boundaries. In so doing he inspired many younger writers. They do not, as they say, make people like that any more.