Recent days have seen Dick Cheney and Tony Blair point belligerent fingers at Tehran, but both spoke in the slipstream of Bernard Kouchner, who a month ago warned the world that it should prepare for war over Iran's nuclear programme. "We have to prepare for the worst, and the worst is war," said the French minister of foreign affairs. The swell of rhetoric - which culminated in President Bush's assertion last week that a nuclear-armed Iran could provoke a third world war - is gravely undermined by what Sir John Holmes, the UN's emergency relief coordinator, has called the "taint of Iraq", and the weapons of mass destruction pretext for invasion. Why should we believe the US and its allies now, when we were already so brutally deceived?

There is, however, another aspect of Kouchner's warning that is much more worrying. When the newly elected French president, Nicolas Sarkozy, nominated Kouchner, the great humanitarian, as the head of Quai d'Orsay, even some of Sarkozy's critics hailed this as a pleasant surprise. Now the meaning of this nomination is clear: the return of the ideology of "militaristic humanism". The problem with militaristic humanism resides not in "militaristic" but in "humanism". Under this doctrine, military intervention is dressed up as humanitarian salvation, justified according to depoliticised, universal human rights, so that anyone who opposes it is not only taking the enemy's side in an armed conflict but betraying the international community of civilised nations.

This is why, in the new global order, we no longer have wars in the old sense of regulated conflict between sovereign states in which certain rules apply (the treatment of prisoners, the prohibition of certain weapons, etc). We instead confront violations of the rules of universal human rights; they do not count as wars proper, and call for the "humanitarian pacifist" intervention of the western powers - especially in the case of direct attacks on the US or other representatives of the new global order. One can hardly imagine a neutral humanitarian organisation such as the Red Cross mediating between the warring parties, organising the exchange of prisoners, and so on. For one side in the conflict already assumes the role of the Red Cross - it does not perceive itself as one of the warring sides but as a mediating agent of peace and global order.

The key question is, thus: who is this "we" on behalf of whom Kouchner, Blair et al are speaking? Who is included in it and who is excluded? Is this "we" really "the world", the apolitical community of civilised people acting on behalf of human rights? We got an unexpected answer (or, rather, a complication) to this question last week, when, in defiance of pressure from the US, Turkey's parliament overwhelmingly granted permission for its government to launch military operations into Iraq in pursuit of Kurdish rebels. Syria's president, Bashar Assad, while visiting Turkey, declared his support of Turkey's right to take action "against terrorism and terrorist activities".

With the likelihood of Turkey launching a cross-border attack under the banner of the war on terror growing by the minute, it is as if an intruder has gate-crashed the closed circle of "we", the domain of those who hold the de facto monopoly on military humanitarianism. What makes the situation unpleasant is not Turkey's "otherness", but its claim to sameness. What such a situation reveals is the set of unwritten rules and silent prohibitions that qualifies the "we" of the enlightened humanity.

It is not the first time Turkey has been a thorn in the side of the cosy western consensus. The crisis of the EU today springs to a large degree from its would-be member. According to polls, the main reason for no votes at the ill-fated referendums in France and the Netherlands was opposition to Turkish membership. The no can be grounded in rightist-populist terms (no to the threat to our culture, no to immigrant labour), or in liberal-multiculturalist terms (no to its treatment of the Kurds, no to its record on human rights). The Turkish problem - the perplexity of the EU with regard to what to do with Turkey - is not about Turkey as such, but the confusion about what is Europe itself. The impasse with the European constitution, and European leaders' efforts to persuade their electorates that the treaty agreed last week does not need a referendum - is a sign the European project is now in search of its identity.

In his Notes Towards the Definition of Culture, the great conservative TS Eliot remarked there are moments when the only choice is the one between sectarianism and non-belief, when the only way to keep a religion alive is to perform a sectarian split from its main corpse. This is our only chance today: only by means of a "sectarian split" from the standard European legacy, by cutting ourselves off the decaying corpse of old Europe, can we keep the renewed European legacy alive. The task is difficult, it compels us to take a great risk of stepping into the unknown, yet its only alternative is slow decay, the transformation of Europe into what Greece was for the mature Roman empire, a destination for nostalgic cultural tourism with no effective relevance.

· Slavoj Zizek is international director of the Birkbeck Institute for the Humanities

szizek@yahoo.com