\The drama in three acts has shocked Europe. First came the killing of three soldiers of North African origin in Toulouse and Montauban, in southwestern France, with no clear link between the two acts. Then followed the murders of three children and one adult at a Jewish school in Toulouse, and fear of a "lone wolf", perhaps a neo-Nazi, gripped the nation. Finally, there was the long siege at the suspect’s home and the revelation that he was a 23 year old Islamist, a purse-snatcher who had turned into a fanatic and a killer.

If the murderous history of Mohamed Merah has any echo, it is because it combines elements inherent in contemporary societies: fascination with a serial killer; the old spectre of anti-semitism and the new one of Islamophobia; increased media coverage of real-life crime stories, the will to control society to prevent acts of terror; the search for common ground between indigenous populations and immigrants over the past half-century – and of course, with the French election campaign in full stride, the political haymaking out of such events.

This is the standard against which we will have to observe, in the short term, how the campaign in France will continue, and, over the long term, what measures will be put in place. Because already the French left is accusing the intelligence services of failing to stop Merah, and President Nicolas Sarkozy is proposing to criminalise visits to extremist websites.

Just like Le Monde, which is usually measured, politicians seem to think that Merah’s murder spree raises the question of a terrorist threat, particularly from al-Qaeda. But there is no evidence yet that the young man from Toulouse, despite his travels in Afghanistan and Pakistan, belonged to an organised terrorist cell. His actions rather seem to reveal the persistence of a radicalised fringe of young Muslims born in Europe but at odds with European society who are driven to act for reasons that are unpredictable and therefore difficult to foresee with any accuracy.

Once again there arises the question of what the British called the “home-grown terrorists" following the London bombings in 2005, and of what means to use against terrorists who, sometimes, do not emerge from traditional terrorist circles.

The first question requires an open, tolerant but frank debate on how European societies should accept a religion, Islam, that has its place in Europe, while refusing to accept extremist behaviour that feeds hatred and mistrust. But this debate must include recognising the inequalities suffered by many descendants of immigrants (and even European citizens), at school and in finding work. It should also include lessons on fighting racism and right-wing violence. European values must be imposed firmly and equally on what La Stampa called “opposing nightmares”.

The second aspect must be vigilance and consistency when to comes to individual liberties. Vigilance, because monitoring communications and Internet browsing is no more acceptable today than it was after September 11. Consistency, because we cannot on the one hand defend individual liberties and on the other demand omnipotence from the intelligence services.

The debate on protecting personal data has been raging for years among some states, their justice systems, the European Commission, the European Parliament, and among human rights and internet user organisations. It should not be shut down by a real, but vague, terrorist threat.