At its heart is a thoroughgoing intellectual debate – about as serious as they come. Two heavyweights fall out over the threat of Muslim extremism, and the way the West should respond. The protagonists square up to each other deploying fine language, seasoned with personal abuse and the odd shot of vitriol. It should by rights take its place alongside those classic confrontations of the 20th century: Bernard Shaw challenging G. K. Chesterton on the State versus the free market; George Orwell accusing pacifists of being pro-Fascist; Bertrand Russell advocating a nuclear attack on Soviet Russia.

But Martin Amis and Terry Eagleton have lost track of the argument. Here were voices from the maverick Right and the Marxist Left, grappling with the nature of Islam and American imperialism, and trying to decide which are the fundamentalists. Instead it has become something entirely different – a question of racism. Professor Eagleton began it with a curious attack on Amis’s father, Kingsley, as a “racist, anti-Semitic boor, a drink-sodden, self-hating reviler of women, gays and liberals”, and going on to charge the son with inheriting some of those traits: “Amis fils has clearly learnt more from him than how to turn a shapely phrase.”

Amis responded by describing the Eagleton sideswipe as “the corniest and laziest secondhand response to Kingsley’s work”. He then took an intriguing diversion, by questioning his own racist instincts, and in the course of it, the extent to which we all harbour racist inclinations. Being an Amis, he went one step farther.

Could the racist gene be gradually bred out, he wondered? His own grandfather, he said, had been “a burbling, bumbling racist” who had been astonished to see black people driving cars in Washington. His father, Kingsley, had harboured mildly anti-Semitic feelings; and he himself, though “pretty free of racism”, still had “little impulses, urges and atavisms now and then . . . Our tribal instincts have been with us for five million years, so to snap your fingers and say you have grown out of that is idle.” He held out the hope, however, that his children would be even less racist than he was. “Their children will be less racist than they are, and so it goes on.”

It is an intriguing idea, though sadly short of hard proof. Genetics tend to work the other way round, with characteristics handed on undimmed down the generations. Darwinism would surely tend to reinforce the self-defensive tribal element in each of us rather than the reverse, seeing the influx of an alien species as a distinct threat to our security. Only education, and the rational acceptance that society has to be inclusive to survive, is there to counteract our atavistic instincts. It may well be that middle-class families are better at teaching their children such things, but nothing about the urban gangs of young white men who terrorise some areas of our inner cities suggests that the hatred gene is steadily being bred out – and it is among the younger generation of Muslims that the extremists are found.

All we can hope is that civilised societies get better and better at reminding successive generations that, unless racism is held in check, the holocaust beckons.

All of which makes the debate about Muslim extremism so delicate – and so vital. By exploring the tenets of Islamic teaching, and demonstrating the way in which the teachings of the Prophet have been perverted, Amis has performed an important service. His essay The Age of Horrorism picks its way through the arguments about the limitations of Islamism and shows how moderation has all too often been buried by those who see their faith as a weapon of revenge against the West. “Naturally we respect Muhammad. But we do not respect Muhammad Atta (the 9/11 bomber),” he writes, adding: “Millennial Islam is an ideology superimposed on a religion – illusion upon illusion. It is not merely violent in tendency. Violence is all there is.”

All might have been well if he had left it there. But in a subsequent interview he expressed a view about how the extremists might be curbed. Perhaps, he ruminated, Muslims might have to face the curtailment of some of their freedoms, be denied the right to travel, be deported in certain circumstances, strip-searched perhaps, until they started educating their children to be more civilised.

Eagleton, not surprisingly, leapt on this. Assuming that Amis’s remarks had formed part of his original essay, he accused him of descending to the level of the British National Party. “There is something rather stomach-churning at the sight of those such as Amis and his political allies, champions of a civilisation that for centuries has wreaked untold carnage throughout the world, shrieking for illegal measures when they find themselves for the first time on the sticky end of the same treatment.”

And so, a debate that might have become serious has descended into cheap invective. Both sides of the argument deserve better. Eagleton, in the introduction to his latest book, explores the question of why the intellectual Left in Britain has failed to mount a serious assault on US imperialism. Amis has written courageously about the way that Islam and terrorism have become conflated. It is a debate that needs to be joined. Perhaps, when they meet at Manchester University, where Eagleton is Professor of English Literature, and Amis is about to become a visiting lecturer, they can get the discussion back on track.

Meanwhile, we are reduced to watching two bruisers knocking spots off each other. It’s enjoyable, of course, but it’s not the real thing.

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