Xenophobia - literally fear and loathing of "the alien", "the stranger", "the foreigner" - has enjoyed a long if inglorious past, not least in Britain.
Across Europe today, and indeed internationally, xenophobic anxieties about "foreign invasion" through migration retain all the political potency they had over 100 years ago, remaining a phenomenon that unscrupulously cynical bourgeois politicians continue to try and harness in order to attain or maintain political power.
Last year, for example, New Labour's immigration minister, Phil Woolas - never a politician who showed signs of original thinking at the best of times - argued that the onset of capitalist crisis necessitated a cap on immigration. This is a classic piece of racist scapegoating straight from the textbook marked "The Beginner's Guide to Divide and Rule".
Xenophobia relates to a wider and ever malleable prejudice against "the other" in general, usually manifested in hostility to the presence of people with unfamiliar cultural norms and customs which allegedly threaten to upset the traditional "way of life" of a particular community. Its focus on "cultural difference" makes it an ideal form for modern racism and bigotry to take.
Modern racists talk of the coming "clash of civilisations" and threat to "cultural identity" posed by not only Muslims but also those of the same skin colour as themselves, for example migrants from Eastern Europe. The "different culture" being objected to inevitably belongs to the poor and powerless.
Indeed, the most ferocious xenophobia tends to occur where the immigrant communities themselves are so minuscule that inventions about their alleged misdeeds can pass without challenge precisely because direct experience of the community in question is all but absent.
One thinks here of the small besieged Muslim community in Denmark and the racist cartoon affair back in 2006. In Japan from about 1986, in the context of economic stagnation, anti-Semitic texts began to circulate in relatively massive numbers in a country where the Jewish population was and remains microscopically small (about 1,000 people).
While xenophobia, ever since the rise of racism and nationalism, has most commonly been expressed in a prejudice against immigrants, there is a sense in which it has longer and deeper roots, pre-dating the rise of capitalism.
Yet there is nothing "natural" whatsoever about xenophobia - indeed the distinguishing "natural" mark of humans is that we cooperate to work and produce things, that we are "social and political animals". Mass migration has been a common theme throughout human history.
Before the rise of modern communications, in medieval Europe, travellers, peddlers and traders were valued by peasant communities as they often represented the only source of information and news about the outside world other than the preachers of the Catholic church.
Today the rise of modern communications technology, email, social networking internet sites and so on makes communicating with people across national borders and cultural boundaries easier and more "natural" than ever. Yet in both pre-capitalist and advanced capitalist societies xenophobia was and remains a powerful emotive and irrational force which often finds political expression.
If simple ignorance and superstition about the outside world were often the central driving force of xenophobia before the rise of science, what explains the continued reproduction of such paranoia today?
The roots of modern xenophobia arguably lie not simply in the monstrous nature of modern nation states with their unrelenting nationalist and racist propaganda from politicians and the media, but also in the competitive dynamic central to the process of capitalist accumulation.
This encourages an individualist outlook and affects not only the capitalist, who is forced to compete against rivals in the marketplace, but also the workers who have to compete for work, homes and so on. Yet unlike the middle class, the common conditions of exploitation which workers suffer tend to force them towards unity and into collective organisations in order to defend their shared interests against capital.
As a result, workers have what the Italian Marxist Antonio Gramsci called a "contradictory consciousness", with "common sense" ideas of race, nation and individual competition sitting uneasily alongside "good sense" ideas of class, internationalism and collective action. As Gramsci noted, workers' resulting personality is "strangely composite: it contains Stone Age elements and principles of a more advanced science, prejudices from all past phases of history at the local level and intuitions of a future philosophy which will be that of a human race united the world over".
Which consciousness carries most weight depends on many factors. But it is only through class struggle, when workers grasp a sense of their collective power, that the humanist "good sense" really surges to the fore. For Karl Marx, whose personal motto was "Nothing human is alien to me", revolutionary upheavals were necessary to finally get rid of all the "muck of ages" that have kept humanity divided for so long. But above all, politics is always decisive as to whether society takes a step forward towards socialism, or a lurch backwards into the kind of barbarism which so scarred the 20th century.
At times of great economic, political and ideological crisis such as that we are experiencing today, two possible alternatives based on collective action present themselves more forcefully than ever - either a class struggle to ensure it is the rich and powerful, those responsible for the crisis, who pay for it - or a xenophobic struggle between sections of the working class for those jobs still on offer. It is not difficult to see which option our rulers would prefer. Socialists must organise to ensure the ruling class, and the politics of xenophobia, are finally consigned to where they belong: the dustbin of history.
"Migration, Migrant Workers and Capitalism" by Jane Hardy in International Socialism 122; Thinking the Unthinkable: The Immigration Myth Exposed by Nigel Harris.