The events in Paris have shocked the world. The cold-blooded attack on free speech has served as yet another warning that there really is evil out there, that we live in a world where no act is too depraved, too morally repugnant, to be justified by some "cause" or other.
For many in Northern Ireland, the carnage will have brought back painful memories. Even for those directly spared the harrowing griefs of the Troubles, there will have been a fear-tinged nausea.
How often did we watch the fractured images of 'breaking news' on TV? The police tickertape fluttering, the eyewitness accounts of the traumatised, the angst and inadequacy of words - whether they be those of journalists, politicians, churchmen or "experts"?
Darkley. Ormeau Road. Greysteel. Claudy. Enniskillen. Monaghan and Dublin. Shankill.
Those atrocities may not have had the epoch-defining significance of the attacks on the Charlie Hebdo offices and the Kosher supermarket but we know the pain the French are feeling today.
And we know their fear. And also the fear of fear.
We don't like to talk publicly about this now. After Paris, we could have asked any number of those among us 'Tell me, what makes someone shoot someone dead at their work in a modern city?". But we didn't, presumably because we wouldn't think it nice or polite.
Even the moving solidarity of the French as they gathered across the Republic had a familiar feel.
How often did we gather - whether for comfort or in defiance - to show how we felt? How often did we look to our leaders to speak for us?
Now, there are clear differences between the French and ourselves. Today, the French are seeking to defend a noble universal principle - freedom of speech. Yesterday, we were engaged in a squalid civil conflict where we justified killing our neighbour in the name of history, identity and community. Our conflict was about getting one up on the other side.
Millions of French people have made their stand and undoubtedly that unity will steady the nerve a little. But then - as we saw here all too often - the crowd will disperse, the feelings will atomise and individuals will go home to their cities, towns and villages. And in their isolation they will feel despair.
They will despair - as we know only too well - because of two things: first, the terrorists won't stop because in their ideological certitude the wishes of the mass can be ignored, indeed must be ignored. Whether they are in search of a worldwide caliphate, a united Ireland or an Ulster lost in the mists of time, the terrorist has already decided that the ends justify the means.
But secondly, and worse, will be the dawning realisation that these terrorists didn't drop out of a clear blue sky. That the condemnation and the horror is NOT universal.
That fact is going to be incredibly hard to bear. It's not surprising that we find it hard to look reality in the face. Within hours of the Charlie Hebdo shootings there were cards doing the rounds of cyberspace showing the horror outside the building with one Kouachi brother tagged "This is a Terrorist" and the fallen policeman tagged "This is a Muslim". The card was a well-intentioned attempt to derail a mass backlash against Muslims. However, it also falsified the truth. The card should have read "This is a Muslim Terrorist" and "This is a Muslim".
Just in the same way we should have had the moral courage to point out "This is a Republican/Catholic Terrorist" or "This is a Loyalist/Protestant Terrorist".
Just like Cherif and Said Kouachi and Amedy Coulibaly, the perperators of our mass murders didn't come from nowhere. They came from us. They may have been warped with hatred but in them we could still recognise something of ourselves.
That's not to say that the majority of people revelled in death and were ardent supporters of heinous murders. Just like the vast majority of French Muslims today, most of us were horrified at what was done in our name.
But… and this is the difficult point that we still can't accept… there were enough providing guns, logistical back-up and, most importantly, emotional and cultural support to allow them to continue.
Some of us knew precisely what our terrorists were up to and decided to keep schtum - and some kept quiet not just out of fear. Some just floated above the moral sewers that ran through both communities knowing they were there but steadfastly refusing to look down - or worse thinking that our atrocities were bad but that the other side's were worse.
The shocking truth is that more than an isolated handful of our citizens supported the death and destruction. A turn on, it gave purpose to their banal lives.
What did you do during the war, daddy? I cheered them on.
Rest assured there will be someone cheering on the comrades of Cherif and Said Kouachi and Amedy Coulibaly.
Marches or no marches.