What are ordinary people to do? How are we to react? What are we supposed to think?
My immediate reaction to the tragedy in Paris was numbness, even dizziness. I don’t know the city well, but I love every inch of it that I do know.
My wife and I have celebrated special occasions there, travelling on the cheap and walking for days around its wonderful galleries and museums.
There is nowhere in the world quite as special as the Musee d’Orsay, no experience in the world quite as special as dinner in the Brasserie Lipp.
Sitting outside a café in Montparnasse or gazing down from the cathedral at Sacre Coeur are unforgettable and affordable moments in anyone’s life.
Sitting outside cafes, on their way home from work on a Friday evening, is what Parisians do.
They talk and argue and laugh. Along the way, they promote a culture of value, one that argues for harmony and openness.
Cultures mix easily outside these cafes – and sometimes great literature or timeless philosophy is born there.
The theatres and music halls are the same. Smoky, atmospheric places where particular types of music, comedy and vaudeville were born. Maurice Chevalier started his career in the Bataclan Theatre.
Edith Piaf and Charles Aznavour sang there at the beginning of their careers.
It had become a rock venue — Jeff Buckley recorded a version of Hallelujah in the theatre (it was later played, ironically, in Fenway Park, Boston, to honour the victims of the marathon bombings before a Red Sox game).
It’s not for nothing that Paris is known throughout the world as the city of love. On Friday night it became a city where mindless brutal hate took over.
It is entirely incomprehensible that people who sit outside a café, or go to a concert or a football match with their children, could be seen as targets for cold-blooded, merciless killing.
Innocent, happy ordinary people were cut down in hails of bullets, or dismembered by bombs to the point where identification was only possible through DNA fragments.
How is that possible? And what are we, the rest of the ordinary people, to do?
What is the world to do?
One ordinary Irish man — actually an extraordinary man —reacted immediately.
John Doyle is the conductor of Co-Orch Dublin, an orchestra that comes together frequently to play glorious music and to introduce new music to the world.
They’ve played in the past to raise money for Barnardos and for the Immigrant Council of Ireland, among others.
In the immediate aftermath of the tragedy in Paris, John posted on Facebook that music was the only response possible.
Within hours dozens of musicians and singers had volunteered their time and talent, and the Concert for Paris will take place on Friday evening In Dublin.
As I write this there is still no venue, but hundreds of people will want to be there, to show their solidarity with the dead and the hurt.
And of course there are dead and hurt far beyond Paris. Hundreds of people have died in the Lebanon, in Syria, in Egypt and in many other places.
The war of terror that is being waged in the name of some unknowable God has no compunction about who, and how, it kills.
All weekend I have been reading commentary about where this has its roots, and there are many who find it easy to blame the West for its policy mistakes – and its own use of warfare – over the years.
But now, surely, is the time for the Islamic and the non-Islamic world to unite against what I heard one Muslim cleric describe as a sick ideology.
ISIS seems to operate as a sect, one that is prepared to sacrifice everything to its own objectives, and one that values no life at all.
I don’t know how it is possible for any group or individuals to enable themselves to kill indiscriminately — the way they did in Paris, and then to blow themselves up, rather than be caught.
The casualness, almost the mundanity of the way they went about it, is beyond understanding.
The only way they win is if they succeed in deepening the wedge that already exists between the West and Islam.
That wedge is of course rooted in history and in recent wars — wars opposed by many in the West but waged in the belief that they would strengthen the stability of the West.
The people who died in Paris died in vain if the world can’t find a way to stop this. Whatever it takes, now is the time for the world to seek to agree that there must be a new beginning.
The leaders of the world — Putin and Obama, principally — have to seek to put their differences behind them to confront what could well become an existential threat.
Even more importantly, Islamic and non-Islamic leaders throughout the world need to come together to find new ways of promoting mutual respect.
I know that sounds banal.
There are many experts on the Middle East who will say that hatred and division runs so deep that there is simply no possibility of building a new political architecture in the region, and therefore no possibility of ending the age-old conflict in the region.
That may be so, and I am certainly no expert in the politics of the Middle East.
But effective peace-building strategies start with removing violence as a mechanism. It can be replaced by political means, and it has happened in other intractable conflicts.
But only when everyone who is willing to talk to each other does so.
In the case of ISIS, it may well be the case, at least in part, that an agreed military response, including the dreaded “boots on the ground”, to capture the ISIS strongholds in Syria and Iraq, is necessary in the first instance.
Most of the victims of ISIS up to now – men, women and children – are themselves Muslim. ISIS regards no-one as an ally or friend.
Their cancerous tactics seem capable of only one response.
But as we mourn the people who died in Paris, and as we seek to demonstrate our solidarity with the capital of “liberty, equality, and fraternity”— values that have never been as important — we cannot do it in the belief that simple revenge will suffice.
No-one who believes in the values the French republic gave to the world can argue that it would be right to see Islam as the enemy, or to see this as a war between two global philosophies.
Again and again I come back to images of Paris — its churches, its cafes, its atmosphere — and I’m haunted by the thought that no-one who died on Friday night deserved what happened to them.
And another thought — with violence as blind and as cold as that — what future can there be if the great powers can’t put aside their own strategic differences to unite against it?
ISIS would, if they were allowed to do so, start a third world war, in which one way of life would be pitted against another.
They cannot be allowed to succeed in doing that.