Visiting the UK, after eighteen months in Eastern Europe, I have been struck by the easy-going multiculturalism that is Britain. Whether in London, Bristol or Liverpool, the three cities on my itinerary, recent immigrants from the European Union – from France and Spain as well as Poland and Romania – mingle comfortably with Black, Asian and white British citizens. Culture, ethnicity and even religion are rarely, if ever, obstacles to harmonious engagement at various levels.

Britain’s and Western Europe’s hard-won and comparatively recent cosmopolitanism should be a cause for celebration. After all, it was less than fifty years ago that Enoch Powell, then a minister in a Conservative British government, delivered his notorious “rivers of blood” speech. Powell predicted violent, inter-communal strife if the numbers of non-white immigrants entering Britain were not curtailed. For the austere, Cambridge-educated Powell, as for many ordinary Britons in the 1960s, people of Afro-Caribbean heritage, even if Christian, seemed at least as alien and unassimilable as Hindus, Muslims and Sikhs, then arriving in their thousands from the Indian sub-continent.

Thankfully, Powell’s doom-laden predictions have not been borne out. Despite isolated and mercifully rare acts of Islamist-inspired terrorism, such as the July 2005 bombings in London and the recent, horrific events in Paris, most people in Western and Northern Europe now regard cultural and ethnic diversity as entirely natural or even desirable. The cultural map of Western Europe, whether in terms of music, literature, food or sport, is scarcely comprehensible without reference to the contribution of iconic figures from the Afro-Caribbean, North African and Asian communities. Britain’s most celebrated living novelist is almost certainly the Indian-born Salman Rushdie, who was raised in a liberal Muslim family.

To most West European ears, the crude, racist rhetoric favoured by several East European politicians, including the Czech President, Miloš Zeman, and Hungary’s Prime Minister, Viktor Orbán, strike a jarring note. In a recent article in the Frankfurter Allgemeine Zeitung, Orbán denounced the mostly Muslim asylum seekers making their way to Germany as unfit to live in Europe:

Let us not forget… that those arriving have been raised in another religion, and represent a radically different culture. Most of them are not Christians, but Muslims. This is an important question, because Europe and European identity is rooted in Christianity. Is it not worrying in itself that European Christianity is now barely able to keep Europe Christian? If we lose sight of this, the idea of Europe could become a minority interest in its own continent.

For most Western and particularly Northern Europeans, “European identity” is an altogether more complex, fluid and variegated phenomenon. In countries that have become overwhelmingly secular, multi-ethnic and multi-confessional in the post-War era, Christianity is just one of several formative influences. For many people, the civilising, rational values of the Enlightenment are of more decisive importance than theistic dogmas and the utterances of biblical prophets.

Europe’s response to the dreadful slaughter in Paris – and to any future terrorist provocations – must be to stand by the twin principles of fundamental rights and multiculturalism. Retreating into culturally and ethnically homogeneous bunkers, the strategy favoured by governments in Poland, Slovakia, the Czech Republic and Hungary as well as by far right parties in Western Europe, would amount to the surrender of the cosmopolitan values that lie at the heart of the European project. It would mark a return to the over-heated chauvinism, superficial religiosity and parochialism of the inter-war era.

Europe’s liberal, multicultural polities must act swiftly and decisively to defend themselves and their values. This will involve pursuing appropriate global strategies, in co-operation with the US, Russia and various regional partners, to contain and roll back the threat posed by ISIS and other Islamist movements. The failure – or in some instances folly – of some previous interventions in the Middle East cannot be an excuse for inaction, as advocated by the Guardian columnist, Simon Jenkins, and others. Europe and European values face an existential threat.

At the same time, Britain, France and the international community have a moral duty towards the civilian population across much of the Middle East. As former mandatory powers, which established the present – and manifestly incoherent – borders of Syria and Iraq, Britain and France bear a particular responsibility for the fate of the peoples of these countries. Britain’s foolhardy and illegal armed intervention in Iraq in 2003, in co-operation with the United States, weakened and destabilised the Iraqi state, while alienating the Sunni minority which had enjoyed a privileged status under Saddam Hussein. This, in turn, has provided ISIS with the opportunity to gain territory and recruits across large swathes of the country.

However, the most difficult and crucial challenge facing Europe will be to address the drift towards radical Islamism amongst elements, however small and unrepresentative, within Europe’s Muslim communities. The thousands of young Muslims who have left Britain, France, Belgium, the Netherlands and other European countries, to fight with ISIS in Syria and Iraq, reflect the extraordinary success of ISIS propaganda and recruitment strategies. At the same time, this underlines the failure of Western Europe to integrate successfully at least part of its Muslim population, leaving a rump of angry and alienated Muslim youth. De-legitimatising ISIS and other Islamist movements, which constitute little more than a perversion of Islam, while pursuing a range of imaginative inclusionary strategies aimed at young European Muslims – such as promoting real non-discrimination in employment policies, the reinvention of civic lessons on common values such as the rule of law and democracy in schools, and wider dissemination of knowledge about Muslim history and cultural values among Muslim and non-Muslim youth – should be prime objectives for both governments and civil society across the continent.