We weep with France today. Tears of sorrow but also, unavoidably, of rage. And behind those tears lies something else: a fearful sense of apprehension rooted in the knowledge that this will happen again, somewhere else. It already is happening elsewhere. The assault on Paris last night followed another Islamic State attack in Beirut in which at least 41 people were killed by two suicide bombers. Near abroad and far abroad; it makes little difference to Islamic State.
The sickening truth about terrorism is that it works. Who can truly feel secure tonight? Who can avoid the creeping dread that this will happen here too? It is only a matter of time. The intelligence services can only do so much; they cannot be perfect all the time. We do what we can but we cannot do everything.
As the statement published by Islamic State makes clear, you may not be interested in war but war is undoubtedly interested in you.
There will be many sage, chin-stroking, warnings against an 'over-reaction' to this atrocity. Of course. And yet it is not possible to avoid reacting to this act of war. Obliterating Islamic State, wherever it is to be found, is not liable to be a sufficient response but it is a necessary part of any response. Because if we did not know before now - and if we did not, it was because we were wilfully denying a grimly observable reality - we know now. There is no compromise that can be struck with the mindset behind these murders.
They may hate us for what we do but, more significantly, they despise us - all the western world - for who we are and how we live. This is so obvious by now that it risks seeming banal but it demands restating because, even now, even after all this, there remain too many people who deny the truth.
And yet if we cannot hide, nor can we run. The suggestion any reaction might contribute to an apocalyptic 'war of civilisations' ignores the reality that this war has already started. It is no more of our choosing today than it was when al-Qaeda attacked Kenya and Tanzania nearly 20 years ago; no more of our choosing than when Islamic fundamentalists murdered Salman Rushdie's Japanese translator more than a quarter of a century ago. Blowback? Get out of here.
Again, as far as they are concerned, this clash of civilisations already exists. All the talk of 'not giving them what they want' ignores the reality they already have what they want. Equally, while it would be grotesque - and counter-productive - to tar all Muslims with some measure of implied responsibility for this carnage it remains equally obtuse to pretend that this is just the result of a perverted form of Islam. Because it is not at all perverted to its adherents; on the contrary they are the chosen few, the holiest of the holy, the best and the bravest. They believe they are carrying out god's work. We cannot respect that but we should acknowledge it.
But therein, perhaps, just perhaps, lies one small sliver of hope, even today, even in the despair and darkness of Paris tonight. This atrocity will not, on its own, be enough to purge extremism inside France or the United Kingdom or Belgium or the Netherlands or Germany or anywhere else. But it must, in time, be the beginning of that overdue purge.
Eventually, we can but hope, radical, fundamentalist, Islam will go too far. It will cross some boundary and be seen to have disgraced itself. For almost all of us - including most muslims - it has already done so; in time that must become clear to those citizens here and in other western countries who are too easily tempted by the purity of extremism. All movements contain the seeds of their eventual destruction; all whirlwinds are exhausted eventually.
That is not enough, not now and not tomorrow, but it is not nothing either.
Awful bargains will have to be struck in the days, weeks, months and years to come. Many of those bargains and accommodations will have adverse consequences and spawn further trouble and heartbreak. They remain unavoidable. International politics necessarily requires triage, dealing with the most pressing problems before moving on to less urgent matters, some of which will themselves be exacerbated by the measures taken to deal with the most urgent crisis. So it is with Syria now. Talk of a 'comprehensive regional settlement' is comfy hogwash. It sounds good but what does it mean and how, in any case, do you get there? Precisely.
Our domestic issues are no less agonising. How can an open society remain open when it is menaced like this? And yet it must remain open; not because failing to keep it such 'lets the terrorists win' or any other such guff but because the alternative is to betray the very virtues and values we purport to be defending. We stand or fall together.
It is difficult to remain phlegmatic today. Of course it is. But remain calm and resolved we must. We have been here before, after all, and despite everything we still stand. That is not enough either, not nearly enough but, again, nor is it nothing either.
And so we beat on and even in the darkness we can find some small moments of solace. As a friend observed, the men of France and Germany slaughtered each other twice in the twentieth century. Last night they were attacked as they met for a friendly football match. This is only a cold consolation today but it is also a reminder that even evil passes. Eventually.