The purpose of terrorism is not to destroy or kill. It is to pursue a political cause through the massive publicity that is attached to terrifying incidents. Today’s bombs in Brussels, apparently related to the attacks in Paris last year and the capture of Salah Abdeslam last Friday, are patently intended to do just that. Merely killing passers-by serves no warlike purpose in itself. The explosive force derives from our reaction to it, from the public attention awarded to it and from the response of the political community. Publicity and response are the terrorists’ “useful idiocies”.

There is no way any community can make itself immune to terror attacks. Since they are random, no protection can defend that community from them. No amount of police work or surveillance, no deployment of armies or navies, let alone of missiles or nuclear weapons, can guard against them. Intelligence and surveillance can go so far, but the bombers and killers will get through any net.

Political terror is as old as war. From the Roman legions to Bomber Command, the instilling of horror in civilian populations has been a standard weapon. “Fighting terrorism” is as meaningless as “fighting guns”.

What is not stupid is seeking to alleviate, or not aggravate, the rage that gives rise to acts of terror, and then to diminish the potency of the incident itself. The first requires a wiser foreign policy than most western nations have shown towards the Muslim world over the past decade. The second is even harder to achieve. It demands patience and restraint in publicising terrorist incidents and in responding to them.

The blanket media coverage assured for any act of violence is reckless. The media must “report”, but it need not go berserk in revelling in the violence caused, as it manifestly has done to Islamic State brutality. More serious, the intention of the terrorist is clearly to shut down western society, to show liberal democracy to be a sham and to invoke the persecution of Muslims. Yet that is the invariable response of the security industry to these incidents. Convinced of its potency, it dare not admit there are some things against which it cannot protect us. So when incidents occur it jerks the knee and demands ever more money and ever more power. It must not be given them.