One must fight both terrorists and the causes of terrorism with the same determination.” That formula, coined ten years ago in the aftermath of the terrorist attacks of September 11, 2001, by leaders as diverse as Javier Solana, then Secretary General of NATO, and US President George W. Bush, is as valid as ever in the aftermath of the recent killing spree in France.The French state managed to identify and "neutralize” the terrorist in short order, though two key questions linger: Should he have been arrested much earlier, and could he have been taken alive? Now the French state needs to go further. French President Nicolas Sarkozy was right to call Mohammed Merah a "monster.” But Merah was our monster. He was born, raised, and distorted in France, just as the terrorists who attacked the London Underground in July 2005 were products of British society.It is imperative, not only for France but for the entire world, to understand how a single, lonely man was able to take an entire country hostage for nearly a week. The only way Merah could find meaning in his life seems to have been to murder soldiers and Jewish children. To kill – and in the most coldblooded manner imaginable – was to exist.Many French initially and secretly hoped that what happened in and around Toulouse would prove to be a repetition of the attacks in and around Oslo in 2011 – that the terrorist would turn out to be the product of the extreme right. Merah claimed to be acting in the name of fundamentalist Islam; in reality, he was the product of a bloody and deviant sect. How can a petty delinquent, a lost child of the French nation, fall prey to terrorist hatred of any variety?The murders in Southwest France reflect three main factors. First, there is the battleground of the Middle East, extended to include Afghanistan and Pakistan. Those problems were not the direct cause of the attacks, but nor were they a mere pretext. The problems of that benighted region act as a particularly dangerous sounding board for alienated Muslim youth in France.Second, alienation is the reality for many French Muslims, aggravated by an economic crisis that has resulted in very high youth unemployment – and that hits young Muslim men particularly hard, retarding their integration within the French Republic.Finally, an identity drift in France may be taking a more serious dimension. Is it purely coincidence that Merah, who was of Algerian descent, chose to act at the very moment that France and Algeria were commemorating the 50th anniversary of Algerian independence?Merah probably felt neither French nor Algerian. He chose what to him passed for a Muslim identity. But it was a perverse, extreme, sectarian version of Islam. Personal issues – the absence of a father or a cohesive family structure – probably precipitated his identity drift. He was looking for a model that could impose some rules on his life, and could not find it until he found terrorism.Confronted with the horror of Merah’s actions, the French nation has demonstrated its unity. By selecting as his targets Muslim and Christian soldiers, as well as Jewish children, Merah strengthened the solidarity of a country that he wanted to divide. But this unity is unstable. The French Republic must recapture its most important lost territories: alienated and fragile young people from immigrant backgrounds.The tragedy has undeniably favored Sarkozy’s campaign to win second term in the presidential election set for April. He was at the helm and acted decisively and responsibly. The political agenda, at least in the short term, has shifted to security, where Sarkozy has a structural advantage compared to his Socialist rival, François Hollande. But, as former British Prime Minister Harold Wilson famously said, "A week is a long time in politics.”Much can change before the first round of the election. What will most concern French voters when they vote? Will economic fears return to prevail over the security agenda? Or will personal factors dominate, with an "anyone but Sarkozy” reflex on one side, and a lack of confidence in the uncharismatic – and possibly unprepared – Hollande. Merah’s savage attacks are a bitter reminder that terrorism still haunts many societies. Security must be strengthened, while its causes need to be addressed. And we will soon find out whether this spasm of terror was just a tragic parenthesis or a turning point.Dominique Moisi is the founder of the French Institute of International Affairs (IFRI) and a professor at Institute d’Etudes Politiques (Sciences Po) in Paris.Copyright project-syndicate.org