Six leading writers will speak on the subject of the Dissident Word in the fourth series of Amnesty Lectures which starts next week at the Sheldonian Theatre at Oxford.

Whatever Gore Vidal has to say in the course of his Amnesty lecture, there can be little doubt that it will be said wittily and well. His calculated wit has been criticised as an ingenious means of skating over thin ice - one reviewer said he had "perfected the art of going nowhere, while being deliciously funny en route". But few deny the man who defined a narcissist as "anyone better looking than you" and who said he was all for bringing back the birch "but only between consenting adults" his standing as a master of the epigrammatic one-liner.

For half a century he has fulfilled the dual roles of iconoclast and scion of America's ruling classes. Like his exact contemporary and political opposite William F. Buckley - also born in 1925 and the other half of a famous televised spat in which Buckley called him a queer and Vidal labelled Buckley a Nazi - he is a critic from within, a satirist with a deadly serious purpose, chipping away at the complacency of the milieu and the nation that produced him.

Politically well-connected -his grandfather Thomas Gore was a senator from Oklahoma while vice-president Gore and ex-president Carter are relatives - he has run for office himself, losing a New York congressional race in 1960 despite outpolling presidential candidate John Kennedy, and polling half a million votes in the California Democratic Primary of 1982.

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But his immense self-confidence rests on achievement as well as birth, with a formidable canon of novels, essays, journalism and scripts built up in the half-century since his first novel Williwaw was published in his teens. Most of his twenties were spent in the shadow of censorship. His third novel, The City and the Pillar, outraged conventional opinion with its portrayal of a college sportsman driven by obsessive love for another male athlete.

He found refuge in pseudonymous crime novels and scriptwriting for MGM. "Censorship was very real in the 1950s and I had a bad time after the blackout. You don't write a movie like Ben Hur if you're having a good time."

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He is a ferocious critic of religion as a constraining force and was denounced as an anti-Christ by television evangelist and ex-presidential candidate Pat Robertson. Along with a disdain for religion goes a fear of the over-mighty state. He contends that the postwar United States has been a "National Security State" and calls for a reorganisation along the lines of the Swiss cantons to take power away from the centre. "The rulers of any system cannot maintain their power without the constant creation of prohibitions that then give the state the power to imprison - or otherwise intimidate - anyone who violates any of the state's often new-minted crimes," he says.

He is perhaps an ironic choice for a lecture series held on university premises. A scourge of current fashions in English departments, he has said: "It is quite evident that, in the English departments of the United States, not only do they not understand imagination, but to the extent that it comes their way they hate it. And they have eliminated literature altogether from the English departments and replaced it with literary theory."