The bomb atrocities in Brussels are a reminder, if any were needed after last November’s jihadi assault on Paris, of how easy it is for terrorist cells to attack neuralgic targets in European cities and bring them to a standstill.

What appears to have been a double suicide attack in the departure hall at Zaventem airport, and an even deadlier bombing in a metro train at Maalbeek station, next to several EU headquarters in the heart of Brussels, killed at least 30 people and wounded around 180 more, some of them critically. The city went into lockdown.

A claim of responsibility on an Isis website indicates this was the work of local cells inspired by their millenarianism, using the Paris model they adapted from a jihadist attack on Mumbai in 2008. The attacks come after last Friday’s arrest of Salah Abdeslam, in a Brussels suburb known for being a jihadi nest, who was wanted as the surviving perpetrator of the Paris carnage. His local accomplices may have brought forward plans to strike Brussels for fear that his detention would lead to their detection.

Such horror calls out for firm but measured conclusions. Europe cannot cocoon itself from the arc of fire to its east and south, the killing fields that run from Iraq and Syria to Libya. That is made obvious not just by terror attacks but the European Union’s inability to act together to deal with the waves of refugees from these and other countries — a dispiriting response that betrays the values of the union.

Brussels is not just the capital of Belgium but of the EU, which is being challenged to show it has the resilience to confront what will be a long and ugly conflict. Isis is making the case for “more Europe” in security.

There are obvious practical measures that need urgently to happen, chief among them better intelligence-sharing about jihadi networks. Belgium, with multiple and overlapping layers of government that do not talk to each other, presents a particular problem. The federal government warned after Mr Abdeslam’s arrest that it might trigger an attack, but was powerless to stop it. But there needs to be far greater pooling of information in real time across the EU and with its allies. After Paris, remember, Mr Abdeslam’s car was checked by police at the French border with Belgium but they seem to have had no idea who he was.

Member states need also to learn more about minority communities and what motivates their members. This is not just about ostensible religious affiliation but the search for identity of some Muslim youth, disaffected and directionless but offered a deranged superhero status by Isis and its ilk. It is chastening to learn Mr Abdeslam, pursued across the continent, was hidden by neighbours for four months.

Above all, the EU and the west need constantly to demonstrate the values they defend, eschewing simplistic bombast and knee-jerk repression. For Donald Trump, the Republican frontrunner to contest the US presidency, Brussels is another brick in the wall he purports to believe will keep Muslims and Mexicans out of the US. For Marine Le Pen of France’s far-right Front National, an attack on the EU capital is an excuse to call for a Battle of Algiers-style razzia — a vast armed police raid — on immigrant “neighbourhoods on the fringes of the Republic”.

Such policies undermine our open societies, built on individual and collective freedoms and religious tolerance. Together they would run up the white flag of surrender. Isis and its acolytes are learning how to tear apart our civic fabric. We need to make that civility more resilient, not do their work for them.