The announcement of the death in Rome of Sir Bernard Williams has struck a heavy blow to British philosophy. Williams was one of the most brilliant figures of his generation and was recognised internationally as a moral philosopher of the first rank.

He helped transform the way in which the subject was practised in Britain and throughout the English-speaking world, but he leaves behind no obvious successor and the nature of universities is now far less accommodating to those whose talents are many, broad, and deep.

Bernard (Arthur Owen) Williams was born in Southend in 1929. After schooling at Chigwell, Williams went up to Balliol College, Oxford, and graduated in 1951. His academic progression was delayed by a spell of National Service spent flying Spitfires with the RAF in Canada. His energy, enthusiasm, and multifarious talents suited him to the task, and the role of fighter pilot further enhanced an image as the brightest of Oxford's gilded youths.

While on leave in New York he met a former fellow student, Shirley Brittain, who was then studying at Columbia University. An interrupted relationship led to marriage in 1955. By that point both were back in England, he having been elected to fellowships at All Souls and New College. Shirley Williams's political ambitions made London their choice of home and he took up positions first at University College and then at Bedford College where he became professor of philosophy in 1964.

His widening philosophical interests were further broadened by encountering at Bedford the complex character Aurel Kolnai, author of the now neglected classic The War Against the West (1938). A Hungarian emigre who studied phenomenology under Husserl and converted to Catholicism on the strength of reading Chesterton, Kolnai brought to moral philosophy both an acute sense of the vulnerability of any civilisation which lacks a serious ethical dimension, and a recognition of the absurdity of confining philosophical thought to any single style or method.

His brand of humane pluralism had parallels with that of Isaiah Berlin (Russian born and culturally Jewish), another important influence from whom Williams learned ''that every thought belongs, not just somewhere, but to someone and is at home in a context of other thoughts''.

Williams had been much admired by his Oxford teachers, including J L Austin, A J Ayer, Stuart Hampshire, and Gilbert Ryle, and they might have assumed that he would carry to new levels their favoured style of close conceptual analysis designed to dissolve, rather than to solve, philosophical problems.

Very soon, however, he began to turn against their ideal of ahistorical abstraction, favouring a more engaged style of philosophising. What he retained, however, was a respect for rigour, which,

combined with his enormous intelligence and speed of thought, made him an unmatchable interlocutor.

Ryle once said of him: ''He understands what you're going to say better than you understand it yourself, and sees all the possible objections to it, and all the possible answers to all the possible objections, before you've reached the end of your sentence.''

The increasing international interest in his work, together with the development of her political career, meant that he and and his wife (later Baroness Williams of Crosby) spent less time together. That, along with a difference of personal style (she relaxed and accommodating, he combative and quick to criticise), and opposition over the matter of religion (she a devout Catholic, he an unwavering atheist) eroded their marriage, the breaking point of which was his relationship with Patricia Skinner, nee Law, then wife of the intellectual historian, Quentin Skinner.

His first marriage was dissolved (and later annulled) and in 1974 he married for the second time. By then he had become Knightsbridge professor of philosophy at Cambridge and had published his first book, Morality: An Introduction To Ethics (1972), followed by a collection of his early and mostly very influential articles, Problems of the Self (1973), and an important published debate: Utilitarianism: For and Against (with J J C Smart).

Over the next 30 years, there were to be further significant books: Descartes: The Project of Pure Enquiry (1978); Moral Luck (1981); Ethics and the Limits of Philosophy (1985); Shame and Necessity (1993); and Truth and Truthfulness (2002); and also further eminent appointments: provost of King's College Cambridge (1979-87), Sather professor of classics (1987-90) and professor of philosophy (1990-03) Berkeley, and White's professor of moral philosophy at Oxford (1990-96). Besides his academic work, he served on several important committees, including the Royal Commission on Gambling (1976-78); the Committee on Obscenity and Film Censorhip (1977-79), of which he was chairman; the Labour Party's Commission on Social Justice (1992-94); and the Independent Inquiry into the Misuse of Drugs Act (1997-2000). He was a member of the Board of Sadler's Wells, later the English National Opera (1967-1986),

and was knighted in 1999.

Williams's philosophical views were always nuanced and defy easy characterisation, but he remained something of a philosophical sceptic and moral relativist, though he was a severe critic of more extreme proponents of these positions.

In Truth and Truthfulness, he attempts to show how abandonment of traditional ideas about the nature and value of truth need not result in intellectual anarchy. Williams's choice of subject for what he knew might

well be his last major publication and the force with which he argues his case may reflect a concern that his earlier

work was widely viewed as lending support to just such a radical conclusion.

Fittingly, upon his retirement from the White's chair, Williams was re-elected a fellow of All Souls, the place of his first academic appointment.

He is survived by his wife and by three chidren: one (Rebecca) from his first marriage, and two (Jacob and Jonathan) from his second.

Bernard Williams, philosopher; born September 21; 1929; died June 10; 2003.