“It is my hypothesis that the fundamental source of conflict in this new world will not be primarily ideological or primarily economic. The great divisions among humankind and the dominating source of conflict will be cultural ... The fault lines of civilizations will be the battle lines of the future.”

With newspaper headlines dominated by the conflict between Israel and the Palestinians, as well as by the confrontation between Pakistan and India, these early lines in Samuel Huntington's 1993 Foreign Affairs essay, 'The Clash of Civilizations', seem more resonant than ever. Huntington, who died on 24 December 2008, aged 81, was a controversial giant among public intellectuals in the United States. He taught at Harvard University for 58 years, founded Foreign Policy magazine and worked in the White House under President Jimmy Carter. Yet he attracted strong criticism from scientists.

In the 1980s, for example, members of the US National Academy of Sciences voted twice to deny him membership. At the heart of the dispute was Huntington's use of mathematical notation as a shorthand summary of complex political ideas, such as his use of equations to claim that apartheid South Africa was a “satisfied society”. As mathematician and academy member Serge Lang of Yale University in New Haven, Connecticut, declared, this gave “the illusion of science without any of its substance”.

That quarrel paled, however, next to the controversy over Huntington's essay. Speculating on conflicts to come in the post-cold-war era, he argued that people ought to be classified as being members of distinct cultures, and asserted that wars can be better understood as conflicts among these 'civilizations', rather than between nations. Most controversial, however, was his suggestion that Chinese and Islamic 'civilizations' posed the biggest potential risks to Western nations.

For many people, including senior policymakers in Europe and the United States, Huntington was saying aloud what they had already begun to believe privately: that to survive and continue to prosper, Western nations need to consider the people of China and the Islamic countries as adversaries. The terrorist attacks of 11 September 2001 strengthened this view, and won Huntington many more converts.

To others, however, Huntington was simply giving academic respectability to the views of ultra-nationalists and religious extremists. The Nobel-prizewinning economist Amartya Sen of Harvard University spoke for many when he argued that classifying humans using a single metric — whether religion or civilization — was not just factually wrong, but also an untested predictor of future conflict. Looking at the historical data, moreover, Malcolm Chalmers of the Royal United Services Institute, a London-based defence think-tank, has found that the proportion of people dying in wars and conflicts has actually declined since the end of the Second World War. And looking at archaeological records of even older conflicts, the economist Samuel Bowles of the Santa Fe Institute in New Mexico suggests that the public-spiritedness and generosity of people today may have come about in part because of a bloodier history of hostility towards outsiders (see Nature 456, 326–327; 2008).

Few, if any, of Huntington's critics could match the simplicity and scope of his original concept.

Elsewhere, anthropologist Arjun Appadurai of the New School in New York says that today's tensions and conflicts are characterized less by a 'clash of civilizations', than by larger groups feeling threatened by smaller ones. This is certainly the case with China's fears on Tibet; India's worries over Pakistan; Israel's dispute with the Palestinians; and the fears among host societies of much smaller immigrant communities. At King's College London, Christoph Meyer and his colleagues in the Department of War Studies have just begun a three-year project that will use this idea to search for ways to provide advanced warning that hostility or antipathy will boil over into violence.

Still, Huntington's clash-of-civilizations idea has had staying power, if only because few, if any, of his critics could match the simplicity and scope of his original concept. Scientists these days often work in highly specialized fields, and tend to be reluctant to propose over-arching theories. Yet policymakers are more likely to respond to people who seem to give the bigger picture, and are able to synthesize it and communicate it clearly.

This is a skill that Huntington had in spades and it poses both a lesson and a dilemma for scientists. Huntington wasn't always right, but his ability to occupy and exploit the space between researchers and its end-users meant that his ideas carried more influence than might otherwise have been the case.