Before we can speak of anything else, we must speak of the victims. Amid all the noise that follows an act of horrific violence, amid the din of debate and argument, it can be easy to stop hearing the pain of the event itself. Paris is mourning the loss of at least 129 people who on Friday were engaged in the harmless, happy business of normal life: eating together, watching football together, listening to music together. Now they are dead, murdered in utterly terrifying circumstances. The survivors, the injured, the entire French people, already wounded by the lethal attacks in January, are reeling from the shock. In their loss, in their grief, in their pain, we are with them.

The French president responded to the Paris killings by branding them a declaration of war. That sounds compelling. To speak of Friday night’s shootings and bombings only as crimes, as if they were equivalent to a string of murders by an urban gang, misses something important. They were co-ordinated, meticulously planned and, according to eye-witnesses, staged with a cold, military precision. Not for nothing did Francois Hollande speak of confrontation with the Isis “army”.

And yet even if Isis did mean this night of slaughter to be a declaration of war, that does not mean France – or the rest of the world – needs to return the compliment. And a compliment it would be. To declare war against Isis is to flatter it, to grant it the dignity it craves. It accords it the status of a state, which Isis claims for itself but does not deserve. It confronts that murderous organisation on terms of its choosing rather than ours.

What’s more, rhetoric of that hue has a recent and unhappy history. In 2001, George W Bush similarly hailed 9/11 as a declaration of war. But the rubric of war, with its implied permission for the most extreme measures, saw the US and its allies make several disastrous decisions. Their impact is felt even now, nearly 15 years later. That category surely includes the forced collapse of Iraq and the subsequent incubation of Isis itself.

Declarations of war pose another problem too: who exactly is party to this declaration? Mr Hollande was speaking for France. But the Paris slaughter also felt like an attack on Europe, maybe even on European values. Yet it’s clear that Isis does not confine itself to that target, attacking instead all who stand in the way of its eliminationist brand of sectarian hate. Last Thursday, a bomb in Beirut killed 43 people. The next morning, a suicide bomber killed more than 20 in Baghdad. Both attacks were attributed to Isis. And just over a fortnight ago, a Russian jet carrying 224 people was blown out of the sky over Egypt, also apparently the work of Isis or an affiliate. And, never forget, the most numerous victims of Isis are not westerners but those Muslims unlucky enough to live within their deathly grasp.

The moral case for Europe to remain a place of refuge is unaltered by what happened on Friday

How then are we to respond? Already there has been a demand, which will only get louder, to change those aspects of democratic and especially European life that make us vulnerable to attack. The urge is understandable. It’s natural and human, when under threat, to want to seal the borders, to halt the tide of refugees, to allow those who would protect us ever greater muscle.

In this climate, it can be unpopular to call for consideration and thought. But if we feel European values are in danger, then the last way to defend those values is by dismantling them. The moral case for Europe to remain a place of refuge is unaltered by what happened on Friday. The allegation that one of the killers came to Europe disguised as a refugee is deeply suspect, the supposed evidence of a found Syrian passport highly questionable. Many of those who fled Syria did so to escape Isis. If anything, those refugees have the potential to be a great asset in the fight against that murderous group.

In Britain, there will be some who see Theresa May’s new investigatory powers bill in a more urgent light after Paris. But unless and until the evidence shows that bulk surveillance would have made a difference in that dreadful scenario, the argument remains where it was. And our starting point is still that mass surveillance of all of us is neither necessary nor effective. When the intelligence agencies are looking for a needle in a haystack, they shouldn’t be adding more hay. When they need to spy on an individual or group, they should seek – and they will usually get – the legal warrant to do so. And, in case it needs repeating, European societies do not defend their values when they turn on their Muslim fellow citizens – on the contrary, they violate those values.

Which brings us to Syria. The defeat of Isis in Syria will not dissolve the threat of jihadi violence, but it is a necessary step on that road. That will surely entail military action, though that does not mean the west has to do all the fighting. Friday’s recapture from Isis of Sinjar in northern Iraq is instructive. The combination of US warplanes in the sky and Kurdish fighters on the ground proved decisive. For all that, the core of the answer must be diplomatic.

Saturday’s talks in Vienna brought together disparate antagonists, including Russia, the US, Iran and Saudi Arabia. But perhaps now – as Russia, for example, has seen that its dogged support for Bashar al-Assad comes at a heavy cost – those nations might finally rise to the occasion. This could be the moment when previously warring interests come into alignment. We urge all the governments involved to seize that moment – for the sake of Syria, for the sake of the innocent dead of Paris, for the sake of our common future.