Samuel Huntington achieved fame as the author of the theory of The Clash of Civilisations. Writing in the immediate aftermath of the Cold War, he predicted that the great upheavals of the future would come from colliding cultures, not rival economic or political doctrines.
Wars of religion would replace the ideological conflicts of the 20th century, with radical Islam mounting a major challenge to the West.
Huntington's forecast may be coming true, but not in the way he imagined. The war in Iraq is turning his theory into a self-fulfilling prophecy. Seeing the American invasion as an attempt to grab Iraqi oil and the images of torture that have come out of Abu Ghraib gaol as part of an attack on Arab culture, Muslims across the world are more hostile to the West than they have been for generations. A full-scale clash of civilisations may not yet be inevitable, but it is no longer a remote possibility.
In the past, wars have rarely been clashes of civilisations. Some of the worst conflicts of the 20th century - such as the first World War and the Sino-Japanese war - were fought within civilisations.
The clear implication of Huntington's theory is that the Islamic world is an homogenous civilisation that threatens the world. In fact, the Islamic world has always been deeply divided - as the savage war between Iran and Iraq demonstrated. The fact is that cultural differences have hardly ever been sufficient to trigger war. Yet today, partly because of the influence of Huntington's theory in shaping the thinking of those in Washington who engineered the war on Iraq, the world is in danger of sliding towards a conflict of precisely the kind he predicted.
If this may turn out to be a tragedy, it is also ironic. The Clash of Civilisations was greeted as a major contribution to the theory of international relations, but its true subject matter was much closer to home. One of the oddities of Huntington's theory is that he never tells the reader what a civilisation is, and this is no accidental omission. Though the book was a worldwide best seller, it was written initially for an American audience. Billed as a study of the emerging post-Cold War order, The Clash of Civilisations was in fact a polemical tract on a domestic American problem - the peculiarly intense conflicts surrounding multiculturalism. The civilisations Huntington sees battling for supremacy in the world are actually American minorities, and his vision of the international system is only American multiculturalism writ large. The irony is that by projecting this parochial struggle onto the global stage Huntington's book has helped make a clash of civilisations a near-reality.
Who Are We? America's Great Debate confronts multiculturalism directly. According to Huntington, American national identity is being dissolved by policies based on the belief that the US is, or should become a cosmopolitan mixture of cultures and ethnicities. Against this, Huntington argues that the core culture of the US is and has always been "Anglo-Protestant". In his view, America is defined by the culture of the colonial settlers who founded it. From the early 17th century onwards this has been the core of American nationhood, but it came under attack from multiculturalism in the late 20th century and at the start of the 21st Huntington believes it is under mortal threat from America's Latino population. Mass immigration from Latin America is tilting the balance away from Anglo-Protestant values and the English language, and in Huntington's view the end-result of this process can only be the destruction of the United States.
He issues a stark warning: "Few people anticipated the dissolution of the Soviet Union and the movement towards the possible decomposition of the United Kingdom a decade before they got under way. Few Americans now anticipate the dissolution of or even fundamental changes in the United States."
It is an apocalyptic vision, but happily it reflects Huntington's over-heated imagination rather than any discernible reality. Scottish devolution and the ongoing peace process in Northern Ireland show that the UK is reshaping itself, not falling apart. As to the former USSR, it betrays an astonishing lack of confidence in the US for Huntington to compare it to that ramshackle totalitarian monstrosity. America's problems may be more serious than most Americans realise, but it has an internal legitimacy the Soviet Union never had and it is certainly not going to collapse.
Contrary to Huntington's doom-laden forecast, the old-fashioned American melting pot seems to be working quite well. There are parts of the US where Spanish is the dominant language, but there is no sign of a permanent "linguistic divide" coming into being that separates America's Latinos from its other citizens. Actually, what we are seeing is the emergence of a country with a majority that will soon no longer be "Anglo-Protestant" but which will still be incontestably American. If America develops in this way, it will only be following a path marked out by other countries. Australia and New Zealand began with much the same "Anglo-Protestant" culture, but have evolved without much difficulty into multi-ethnic nations. Brazil has a complex cultural heritage, but that has not prevented it from developing a distinctive national identity. In the long run, America is unlikely to be much different.
Where the United States differs from these - and all other - countries is in its grandiose self-image.
More than any other country today, America defines itself by reference to universal principles.
Arguing that the core of American culture is a particular historic tradition, Huntington rejects this belief. Instead he identifies American culture with "English traditions, dissenting Protestantism and Enlightenment ideas" somehow not noticing that Protestantism and the Enlightenment are universal ideologies. In fact, it is the exceptional strength of these ideologies that has given the American debate on multiculturalism such peculiar intensity. Huntington's provocative and wrong-headed book is a symptom of the condition it pretends to diagnose.
John Gray is Professor of European Thought at the London School of Economics. His most recent book, Al Qaeda and What It Means to Be Modern, was published in paperback by Faber and Faber last month.
Who Are We? America's Great Debate By Samuel P. Huntington Free Press, 428pp. £18.99