Modern satire is the kind of subject which ought to be easy enough to address. Hardly a week goes by in which some new play or film or novel is called satirical. In the past year we have had Election, about political corruption as filtered through an American high school, and Pleasantville, a satire on the idealisation of 1950s family life. The Channel Four programme on paedophilia for Brasseye aroused huge controversy this summer. Satirical magazines like Private Eye are national institutions. We even have a children's novel I was a Rat by Philip Pullman, using the fairy-tale of Cinderella to probe at the relationship between Royalty and the Press. Satire has never seemed so healthy. Laughter, as Nabokov observed, is the best pesticide. Modern life scarcely lacks pests. The modern satirist can find him or her self surveying the world around and thinking like Clint Eastwood in Dirty Harry "Ask yourself - do you feel lucky, punk?"

But what is this thing called modern satire? Is it really so healthy? How does it differ from the classical kind - the sort some of you may be reading now at school, in the plays of Aristophanes and the poetry of Juvenal? How does it differ from the romp of Tom Jones, Jane Austen's inches of ivory, or Thackeray's Vanity Fair? How has it changed this century as a result of scientific discoveries, the loss of religious faith, the advent of feminism and - not least - the libel laws?

The word satire has its origins in the Latin word satira- meaning a full dish, a farrago or medley - something, in other words, that does not have to be realistic as long as it entertains and provokes. This may be useful when we think of the kind of satire written by people as diverse as Fay Weldon, Tom Wolfe and Jonathan Coe. But it does not help us when we come to think of the satire which approaches tragedy. For satire as a word and as a concept has also, significantly, become confused with Greek satiric drama - which Aristotle believed to be the very origin of tragedy. This too may be useful when we consider darker satirists such as George Orwell, Aldous Huxley and William Golding.

So - is it a feast of farrago, or the parent of pity and terror? Should satire make you laugh or cry? Or do both? We all have a rough idea of satire as being an attack on folly or vice - an attack, which uses mockery, wit and inventiveness against the puffed up and powerful. Satire is like the catapult used by David in his apparently unequal contest again Goliath: it can really even some of the odds, it can sting and madden the big bully who has everyone else cowed. But it can't, alas, kill him. Writers don't have that kind of power. Satire can only make us aware that evil exists, and make people wiser or braver by laughing at it. We may not all have a vision as bleak as Orwell's 1984 (envisaging how, in a totalitarian world, an individual will betray everything and everyone when tortured) but even the more light-hearted like David Lodge knows that the horror of the factory floor as described in Nice Work isn't going to go away.

And yet we know that it is possible for a writer to at least begin to change the world. One of the greatest satirists the world has ever known, Dickens, discovered this when he wrote about the suffering of the Victorian poor, and especially their children. Others such as Huxley, Orwell and Kafka made people aware that the democracy won in the West over the past hundred years exists on a knife -edge. It is worth noting that both Dickens and Orwell were great journalists as well as great novelists. Journalists are usually the first to find out about the way a society is heading, and the circulation of newspapers is so much greater than the sales of novels that they have more power to stir people's hearts and minds. But not only is journalism a transient thing - a big story or scandal is usually here today and gone tomorrow - it often misuses its power. We all know about spin-doctors, those shadowy and sinister figures that try to "spin" the news in a way favourable to the political party employing them. Journalists hate spin-doctors, but they, too, spin the news. (People are always fascinated to see their own vices in others.)

The piece from A Vicious Circle that I read to you at the start is about spinning a book review. It could, however, apply to most kinds of journalism. There isn't one thing that Ivo said to Mary about reviewing that hasn't been said to me by editors of national newspapers. It really can be as silly, venal and careerist as that. There are some good, brave and even great journalists - but very few. There's a rhyme every hack learns when starting to work in the media that goes like this:

"You cannot hope to bribe or twist
Thank God the English journalist
But seeing what unbribed he'll do
Thank God there is no reason to."

The fear or favour market Ivo describes is profoundly corrupting, not least because the very people who most need help from the media so often get ignored by it. When I wrote A Vicious Circle it was with the intention of writing not just a modern satire about London, but a modern version of the Victorian novel - about the ways in which the richest and the poorest of our society are interconnected. For the past hundred years people haven't written this kind of fiction, at least not in this country - Tom Wolfe and T. Corraghessan Boyle have revived it in America. You get middle-class novels about middle-class people - usually committing adultery in Hampstead or the Home Counties - a sprinkling of novels about the upper classes and an equally small number about the working class. Otherwise, novels have become like boil-in-a bag meals, completely sealed off from everything else. I wanted to try and connect these worlds again. And I think I did.

Strangely, very few reviewers noticed this, because the satirical elements about literary London got me into big trouble. A Vicious Circle very nearly wasn't published because a book reviewer - now literary editor of the Evening Standard - violently objected to it and claimed that he had been libelled as one of the characters in it. The original publishers, Penguin, were so terrified by his threats that they promptly stopped publication. Luckily, the scandal this caused meant that another publisher felt brave enough to buy it for a lot more money. But if they hadn't, I could have lost not just five year's work but (if it had gone against me in court) my house and liberty. These are very real threats. Interestingly, of the satirical novels I know of that have been suppressed by libel threats two of the best - Malcolm Muggeridge's The Picture Palace, and Murray Sayle's A Crooked Sixpence - are about the Guardian and the News of the World respectively. Journalists claim to support free speech, and some do: but they are also among the first to suppress it if their own behaviour comes under fire. In the past a classical satirist like Ovid could be exiled from Rome, but he didn't get his work stifled at birth. So in some ways, the modern satirist is in a much more dangerous position.

Satirists are often accused of writing out of a desire for revenge, but no work of art, however minor, can really be produced in this cast of mind. Revenge is a very small, mean sort of thing to want - enough, perhaps, to fuel a short story but nothing more. What does, I think, partly drive satire is anger - what Swift called saeva indignatio, or savage indignation.

It's no wonder, then, that so many of the best modern satirists should be women. You don't have to be a radical feminist to become extremely angry at the way women were until very recently, kept ignorant and powerless, forced into terrible marriages in which all their property automatically became their husband's, and generally made into an underclass. You, as the new generation, probably have only the haziest idea of how recently women's educational chances began to approach that of men. When I got into Cambridge twenty years ago, for example, it was eight times more difficult for a woman to get a place than a man. Now, the numbers are almost equal. In my second job after university I was told by my boss that if I didn't go to bed with him, he'd fire me. That was at around the time you were being born; I don't think a man would be quite so confident now. (I resigned, needless to say.) In the literary world according to Mslexia the excellent new magazine championing women's writing, women buy 65% of all books - but strangely, women authors have just one third the chance a man does of being reviewed in the papers.

There is, in other words, a lot to satirise. Yet satire is still supposed to be the preserve of men. If satire is mentioned you'll hear a lot about Will Self and Jonathan Coe - nothing about us. Like the elephant in the kitchen, women satirists aren't supposed to be noticed or talked about. Only last year two serious, intelligent journalists, Nici Gerrard and Sean French, claimed in The Observer that women neither wrote nor read satire. This is amazing when you think that novelists such as Muriel Spark, Doris Lessing, Hilary Mantel, Jane Smiley, Sylvia Plath, Carol Shields, Helen Simpson - I could give you a dozen more - have all written satire. Perhaps the most famous of these is Fay Weldon, whose brilliant cascade of feminist fantasies - cloning yourself, turning yourself into your husband's mistress by means of plastic surgery and so on - are still hugely popular. Unfortunately, having been cast as a radical feminist twenty years ago, the humanity and generosity in her work are often missed - Hollywood turned the film of Life and Loves of the She-Devil into a revenge story. Revenge, as I've said, is a paltry desire. To write successful satire you need to feel very deeply about, say, poverty, or the oppression of women, or the dangers of genetic engineering - and then have the intellectual control to make your readers laugh as well as weep.

Often the laughter can mask the anger. There is a famous essay on Jane Austen by DW Harding, called Regulated Hatred which you should all read if you haven't already. It claims, pretty convincingly, that far from being the sort of genteel English Heritage romantic many people think, Austen's novels were intended to be read and enjoyed by precisely the sort of people whom she disliked and wanted to undermine. This is quite often the satirist's experience. Unlike her heroine Emma, Jane Austen was neither young, handsome, rich nor married - she lived a life close to that of Fanny Price than Elizabeth Bennet. Harding's essay highlights the dilemma that the female satirist faces.
"She has none of the underlying didactic intention ordinarily attributed to the satirist," he says. "Her object is not missionary; it is the more desperate one of merely finding some mode of existence for her critical attitudes. To her the first necessity was to keep on reasonably good terms with the associates of her everyday life…And yet she was sensitive to their crudenesses and complacencies and knew that her real existence depended on resisting many of the values they implied. The novels gave her a way out of this dilemma."

This goes some way to explaining why women satirists are often overlooked. It isn't just that the arbiters of literary fashion want to believe women are too nice and gentle to be satirical. It's that we suffer from conflicting desires. We want both to be red in tooth and nail, and to please. Very often, the need to make money is more pressing for women than it is for men - that's why we tend to do more journalism - so there is a romantic ending that softens what has gone before. Women also tend to draw their characters with more realism. Jane Austen's caricatures are closer to real life and the way real people behave than, say, many of Charles Dickens's. Perhaps that's why we hate, say, Mrs. Norris in Mansfield Park much more than the witchy figure of Miss Havisham in Great Expectations.

The modern woman satirist is not a lot braver in attacking folly and vice. A novel such as Margaret Attwood's The Edible Woman is a sparkling description of how young women were bullied into sex and marriage by the expectations of the early 1960s - but you can miss the simmering rage simply because it's so funny. Muriel Spark's The Prime of Miss Jean Brodie is harder to get wrong because we learn that the girls' hilariously egotistical teacher, "an Edinburgh Festival all on her own" is a Fascist who admires Hitler. She was apparently based on a real teacher Muriel Spark had, but most schoolgirls seem to recognise some aspects of her in their own schoolteachers. I hope you don't in yours. She is seen most clearly through the merciless eyes of Sandy, who comes close to standing in for the novelist's own consciousness. But Sandy punishes herself for her own loss of innocence - and perhaps, her perceptiveness. After betraying Miss Brodie, she becomes a nun. The women who see too much in satires by women are quite often punished by their authors - humiliated, like Jane Austen's Emma, by their own arrogance, or brought close to madness like Stella in Rachel Cusk's The Country Life. No such fate typically awaits the male protagonist in satires to men. The yobs in Martin Amis's novels survive; so, too do the men in Evelyn Waugh's black comedies - even if they lose their jobs and their freedom. Perhaps you can't write really good satire unless you've been as humiliated as thoroughly as women often are. Men like Dickens, Thackeray and Kafka knew what it was like to be crushed by poverty or their families; one suspects that the men writing satire today just don't. At its worst, satire is just a kind of sarcasm for people with university degrees.

Perhaps women satirists get overlooked because we aren't supposed to have a sense of humour. It's amazing how this notion persists, even with French and Saunders being the only really funny comedians on TV. It is interesting, though, to note how much of women's humour revolves around humiliation. The best male comedians such as Harry Enfield rarely humiliate their personae - Tim Nice But Dim and Tory Boy remain blissfully unaware of just how ghastly other people think they are. They never get taken down a peg, in other words. In women's satire, that's just what happens - just think of how Patsy, Edina and Saffi all take turns to humiliate each other in Absolutely Fabulous. Patsy and Edina wind up in court, crawl through garbage, get snubbed, drunk, overdrawn and hurt. They have a pretty good idea of how ghastly other people think they are, but bounce back because they are too arrogant to care.

This is quite like the humour of the marvellous American satirist, Alison Lurie. As the modern writer closest to Jane Austen, she can really make your heart stop writing immaculate comedy. Like Austen, she makes you feel briefly much more intelligent than you probably are. Her satire isn't didactic either, just unblinkingly observant. Here she is in The Last Resort, her most recent novel, inside the mind of Wilkie, an elderly professor. He is, like all the best characters in a satire, completely blind to his own complacency.

"Several retired professors of Wilkie's acquaintance had moved into Skytop, and when visiting them he had been appalled by their blind complacence as well as their increasing self-centredness. It was clear to him that though Skytop resembled an upmarket motel it had deeper parallels to an expensive internment camp. If you lived there, you couldn't but help be aware that every so often one of the inmates would be taken away to die slowly in what was euphemistically called "a nursing facility." You wouldn't know when your turn was coming, but the longer you stayed, the more likely it would become that you would be chosen. And of course, eventually, everyone would be chosen.">

Wilkie thinks he is dying of cancer of the colon. The fact that this turns out to be piles doesn't lessen the chill of that last sentence. We are all going to be chosen

What we may find remarkable about satires written by women is that they are peopled by characters that are on the verge of stepping off the page and into our hearts. We care about Jane Austen's characters, Stella in The Country Life, and the narrator of Jeanette Winterson's Oranges are not the Only Fruit; we care, horribly, about Sylvia Plath. We don't care about the narrator in Jonathan Coe's What a Carve-Up, or the animals in Animal Farm, or the men in Evelyn Waugh. They make us think and laugh, but not feel. (This is one of the reasons why satire is particularly well-suited to science fiction, as people like Robert Heinlen, Larry Niven and indeed Fay Weldon realised.) In some satirical worlds, making us feel would in fact be unbearable. Yet the great satirists do this, and that is what gives them their power. Interestingly, two of the best new satirical films, The Truman Show and Pleasantville have at their heart the need to feel real emotions - emotions that have been suppressed or faked in the supposedly ideal community. Satire is aware of the importance of feeling, almost by omission.

It doesn't have to be red in tooth and claw. Satire can even be gentle, and refreshing to the spirit. One of the novels I love best is Stella Gibbon's Cold Comfort Farm. It is the wickedest send-up of country life that exists. Few readers fail to cheer on the bossy Flora Poste in her efforts to civilise her uncouth relations the Starkadders. Yet here, too, there is something almost tragic at the bottom of it. Elfine, Flora's protegee, is a mess partly because she wants to write poetry. Flora tells her that if she wants to marry into the upper classes this will simply not do. In other words, she suppresses the artist in another woman because it will make her unmarriageable. Art, you see, does come out of untidiness and suffering, and this is implicitly recognised. It is interesting to note that Stella Gibbons herself came, as you might guess, from a family as prone to emotional violence as the Starkadders. After Cold Comfort Farm, she never wrote another good book. She had got married. Jane Austen never did.

If satire is produced partly by rage, does that make it inferior art? I don't think so. You only have to think of a novel like Bleak House or Emma to see how satire can be great art. The greatest novels - novels like Lord of the Flies, say, or Proust's Remembrance of Things Past - all have an element of satire in them, and this isn't just because their authors had a sense of humour. Ultimately, satire is about justice - the fantasy of justice, perhaps, but justice all the same. We are all capable of using rage constructively. Neither rage nor the desire for justice is something to be ashamed of, and in modern life, with its unparalleled choices between good and evil, between creation and destruction, satire has a crucial part to play in making us both think and feel.

I'd like to end with what the psychotherapist Adam Philips writes about rage in his book, The Beast in the Nursery:

"If anger is evidence of our idealism, our self-idealisation - of just how unconscious, how frantic, our sense of justice is - it also reveals by the same token that our potential for humiliation is the root of morality…Nothing confirms more clearly the impossibility of amorality than our capacity to be humiliated. That we can feel humiliated reveals how much what matters to us, matters to us. Our rage itself is a commitment to something, to something preferred. Indeed, how would a person immune from humiliation know what a good life was?"