The purpose of terrorism is to terrify. In that aim the perpetrators of the attack on the staff of Charlie Hebdo in Paris have been successful. They have shown that journalists in Paris cannot be protected against men carrying heavy weapons willing to kill anyone in their way. Leading journalists and cartoonists, familiar to all French readers, have been gunned down despite Police in the street, bodyguards in the building and locks on the doors. Pens were not mightier than machine guns that day, though they may be in the long run. In the grisly trade of political assassination this has been a successful mission.

The status quo of domestic policing in Europe is that most people are peaceful, and that the few who are violent are doing so for their own limited criminal purposes and want to avoid detection and capture. They run away with their stolen goods, and are usually eventually tracked down. These particular perpetrators of the attack on Charlie Hebdo have already been identified as being two brothers with criminal backgrounds. They have moved on to Posture criminality, in which the aim is to stroll and swagger rather than run, to cause the greatest hurt possible, to be triumphant in murder so as to glorify themselves and their adopted cause. Conventional policing will always have a difficulty when confronted with armed death cults, who kill for the sake of making a larger political and religious point. “Don’t ever make fun of Islam” is their boast, and they are in charge of deciding what constitutes fun.

However, it would, be mistaken to describe these miscreants as “professional”. Professional soldiers follow rules of engagement, and do not kill unarmed civilians or even armed men who are wounded, incapable of defending themselves, and have surrendered. “Dispassionate” or “cold blooded” would be closer to the mark, and even that may be part of a posture, the martyr’s bravado, the swagger of a fool who considers himself fully justified because of a set of arguments which admit no contradiction.

Liberal democracies are a soft touch on these matters, and that is their attraction to the locals and to immigrant arrivals, and also part of their strength. Avoiding over-reaction is a measure of the long-sightedness of a tolerant society. However, there is also a danger in under-reacting. “Business as usual” is a good policy most of the time, but it can also slide into appeasement, withdrawal, and the cowed acquiescence of a fearful public, restricting their opinions and freedoms. What democracies must now work out is how they deal with people who treat open societies as if they were war zones, and who regard their half-examined convictions as being justification enough for slaughter. France and Europe as a whole will have been frightened by this attack. It is not too much to speak of them going through a collective symbolic trauma. However, they should not shirk from recognising that Islam has a prominent militant wing, a death meme which finds resonance in many a self-important young idiot, and with a supportive fringe of unknown size who will condemn the act and then list the supposed causes in the distant sense of “understanding why they did it, wrong as it was”.

After being subjected to criminal and political violence many of my traumatised patients felt that they would never see humanity in the same way ever again. That is understandable, though an over-reaction. Equally, seeing this event as an individual aberration is an error. A corrosive idea is doing the rounds of the impressionable: you are justified in killing those who criticise your religion. Pens also wrote the murderous stories contained in some sermons and religious texts. Pens, and perhaps more, will be required to counter it.