This collection of eight essays spans the range of Isaiah Berlin's interests, including his role in the disputes of language philosophers in the 1930s, his interest in political philosophy and his later attention to the history of ideas. In Berlin's preface to this collection he records his decision to abandon philosophy for history in the 1940s, but by his own definition of philosophy, given in the first essay 'The Purpose of Philosophy', he continued to be a philosopher par excellence, radically questioning the models, or categories, by which human beings understand their world. Berlin sees this as the perennial task of the philosopher, which he recognises as 'agonising and thankless' and one he takes up in this collection with analyses of 'Verification' and 'Equality'. It is doubtful now whether Berlin's view of philosophy would be taken as an exhaustive account of the enterprise, especially with the flourishing in the last 25 years of applied ethics and political philosophy, and it seems reasonable to suppose that philosophy will continue to involve speculative work about the proper ends of human life, as well as logical analysis. Berlin's paradoxical contribution, evident in this collection, was that in committing himself to a life of radical questioning of concepts and categories, he in fact proposed a purpose for life, namely the creation of a society that would not be duped by incoherent and idealistic models of the world. Radical philosophical questioning, that drive for clarity in language and for models of the world that are capable of empirical testing, is not in such circumstances the Sisyphean endeavour it might otherwise appear.