When only a really bad word will do

Of all the taboos in literature, one of the hardest to regulate is the use of four-letter words. There is still, even in the age of Irvine Welsh, a widespread feeling that too much effing and blinding is simply crude, or an affectation - even if it is an accurate representation of the way people speak. But sometimes the mot juste has four letters, and there's nothing we can do about it.

Last week, it emerged that one of the most celebrated lines in the history of the cinema had almost ended up on the cutting-room floor. Even people who haven't seen Gone with the Wind know of the moment when Rhett Butler turns in the doorway and snaps, to the shrewish Scarlett O'Hara: "Frankly my dear, I don't give a damn." Now it emerges that in 1939 this line was thought to be too rude, and was almost replaced by the wonderfully anodyne: "But frankly, my dear, I just don't care." David Selznick, the producer, only managed to appease the board of censors by giving it $5,000.

It wouldn't have been easy to slam the door after a line like that: Rhett would have sounded like a sulky teenager. Indeed, it is hard to imagine a time when such an innocuous curse could have made anyone think twice. These days - in Tarantino's films, for instance - people don't give damns: they give flying fucks. And the fact that linguistic fashions can change so swiftly is bound to make anyone pause before being too dictatorial about modern expletives. It is in the nature of four-letter words that they lose some of their force as soon as they become frequently used. New ones, closer to the edge of offence, have to be found. Swearing, like all aspects of language, is a moveable feast.

It is also a matter of context. When small children swear, we fight to suppress a giggle: it's so sweet. It is only as they age that we start to harangue them. I once took a small boy to a football match, which despite all the talk of gentrification, was still a swamp of traditional Saxon expressions. The man behind us yelled: "Fuck off Leboeuf you fucking Frog cunt," for about an hour and half. Yet we all laughed easily when the four-year-old asked politely: "What's a fucking referee?"

Swearing is political as well as literary, a matter of substance as well as style. Someone once remarked that a language was simply a dialect with a navy, and the foul-mouthed characters who swear their way through James Kelman's novels (inspiring an entertaining controversy when he won the Booker Prize in 1994) are given a deliberately angry vernacular. But you only have to read them aloud to see that they are not remotely realistic: this is swearing as rhetoric, and Kelman has poetic motives: he is dramatising the stricken cry of his excluded or hapless characters. Intriguingly, a writer like Roddy Doyle can shite his way through book after book without attracting the least abuse, since his slangy idioms are sweetened by benign comedy.

Tony Harrison also found himself in warm water when his poem v recorded the ripe curses scrawled on his parents' gravestones in a Leeds cemetery. The title was a nice triple pun: it stood for versus (as in Manchester United v Leeds) and for verses; but it also stood for the classic two-fingered salute. Harrison seemed to enjoy noticing the irony in the fact that many of the people most vexed were also the quickest, say, to welcome bombing campaigns - as if bad language were a greater breach of civilised etiquette than missiles. Swearing is demotic; it is the way people talk, even though they know they're not supposed to. So to swear is always slightly rebellious or anarchic: that is why it makes us squirm a bit. Newspapers continue to be reticent, especially the so-called "family" newspapers that seek to scandalise us by entrapping celebrities in sex or drugs "sessions". It is almost a paradox: readers perfectly tolerant of all that sleazemongering act all offended when confronted by oaths they themselves use on a daily basis.

George Steiner once claimed that modernism began on the day Virginia Woolf dropped her teaspoon and said: "Fuck". Certainly, the original complaint against Ulysses was based on the author's earthy language - ironic, given the weight of the novel's classical allusions. One of modern literature's most urgent tasks has been to remind us that art is impolite, that books can do something more than furnish a room. This doesn't mean to say that bad language is a good thing: any number of crap books lean on the f-word in order to seem street-credible, or simply to shock. But sometimes - I'm sorry, but nothing else will do. Curses are the tracer bullets of our language. They are unlovely, but not everything in life is lovely. And when the need arises, we wouldn't give a XXXX for anything else.