In one corner is the bow-tied, genial writer of detective stories which have become one of the surprise literary hits of recent years. In the other, the foul-mouthed, bullet-headed hardman of cutting edge contemporary fiction.
About the only thing Alexander McCall Smith and Irvine Welsh share is their Scottishness and, so far, they have been content to operate from almost opposite ends of the fictional spectrum. But now McCall Smith is accused of firing a literary salvo at his countryman, saying that writing is a "moral act" and suggesting that novels by the Trainspotting author - with their depiction of drug-taking low life on Edinburgh housing estates - have debased the image of modern Scotland.
He was quoted in an interview published in a South African newspaper as saying that publishers should reject "aggressive, vulgar" authors.
"I've got no time for that," he said. "I've got complete contempt for that. I feel that writing is a moral act. I feel that those who portray an aggressive, vulgar, debased attitude towards life are conniving in that life, and I think publishers should reject them. I think Irvine Welsh has been a travesty for Scotland. It portrays a notion of Scottish miserabilism. But most people in Scotland aren't like that ... they don't behave like that."
However, last night his spokeswoman Jan Rutherford insisted McCall Smith had been misquoted and misrepresented in the interview and that he would now be writing to Welsh to point this out. A statement from the author said: " All that I said was that I did not agree with that vision of Scotland that he represented. Some people take that view and that is up to them. It is a storm in a tea cup, I have nothing against Mr Welsh. I do not know him and I believe that he is a perfectly reasonable and charming man."
McCall Smith, a Scottish Presbyterian, also criticised D B C Pierre's novel, Vernon God Little, the winner of last year's Booker prize, for its liberal use of expletives. He stressed he could never allow any of his own characters to use profane language. He said: "It's an act of verbal permissiveness and sexual aggression. I will not do it and I've got no time for it. It sounds terribly pompous but it's true."
McCall Smith's experience of Edinburgh is very different from Welsh's. A law graduate from Edinburgh University, McCall Smith is now its professor of medical law and is also deputy chairman of the Government's Human Genetics Commission. Home is a large house in a leafy suburb. He began writing 20 years ago and is now the author of more than 50 books, but it is only in the past five years that he has enjoyed major success with his novels featuring Precious Ramotswe, a Botswanan private detective, who relies on good humour and common sense to solve her cases.
Relying on McCall Smith's experience of growing up in Zimbabwe, where his father was a lawyer, they have been praised for their upbeat image of Africa and have been published in 26 languages. Worldwide sales have topped three million and the US first lady, Laura Bush, counts herself as a fan. Anthony Minghella, the Oscar-winning director, is said to be keen on making a film version of The No 1 Ladies' Detective Agency, the first book in the series.
Welsh's first novel, Trainspotting, notable for its lengthy strings of expletives and use of almost impenetrable Edinburgh jargon, was published in 1993 with an initial print run of 3,000 copies. But it went on to become a cult hit and was filmed with Ewen McGregor and Robert Carlyle. He has since followed it with a series of books on similar themes.
WORLDS APART: AUTHORS AT ODDS OVER MORAL MAZE
ALEXANDER McCALL SMITH
THE MAN: Morally upright and Presbyterian, yet convivial and donnish. Expert on medical law and ethics.
BOOKS: More than 50, ranging from children's stories to a study of sleep. Success with stories of female private detective in Botswana. Lots of the crimes are committed by animals.
FAN BASE: Laura Bush. Which just about says it all.
QUOTE: "The problem, of course, was that people did not seem to understand the difference between right and wrong. They needed to be reminded about this, because, if you left it to them to work out for themselves, they would never bother. They would just find out what was best for them, and then they would call that the right thing. That's how most people thought." - THE NO 1 LADIES' DETECTIVE AGENCY
THE MAN: Working-class, foul-mouthed literary roughneck. Arrested for drunkenness at football match in 1996.
THE BOOKS: Written in the dense and expletive-heavy argot of the Scottish housing estate, they depict a cast of low-life characters. Lots of drink, drugs and sex.
THE FAN BASE: Fashionable literary types, most of whom have never been near a heroin-riddled housing estate.
THE QUOTE: "Some ruling-class cunt, a junior minister or something, says in his Oxbridge voice how Billy wis a brave, young man. He wis exactly the kind ay cunt they'd huv branded as a cowardly thug if he wis in civvy street rather than on Her Majesty's Service. This fucking walking abortion says that his killers will be ruthlessly hunted down. So they fuckin should. Aw the wey tae the fuckin Houses ay Parliament." - TRAINSPOTTINGReuse content