The simplest and most important thing that we need to remember in the days ahead may also the most easily forgotten: Senseless acts of violence are just that – senseless. There is no greater message, no deeper political context.

Someone opened fire at Pauline Marois' victory rally Tuesday night with horrible results. Every Canadian grieves.

Evil stalks the most peaceable kingdoms: Sweden. The Netherlands. Canada. The people who turn guns on the innocent sometimes claim to be acting in the name of a higher cause. But there is no cause.

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Yes, terrorists often act with cold calculation in pursuit of a political end. We have witnessed the carnage the followed, from a Serbian nationalist who helped ignite the First World War by assassinating a crown prince, to the savage attacks on New York and Washington whose anniversary we will commemorate in six days.

But unless there is some lunatic sect that has this far escaped detection, we may assume this attack is the kind of personal assault that has become so frighteningly common in our time –someone turns a gun on innocent students, or a politician, or those between him and a politician. Such people may invent a grievance in their own mind.

People sometimes look to outside causes for failures inside themselves. They blame "them," whoever they are – within their own family, their workplace, or the public square. They may blame their spouse, or their coworkers, or the Christians or the Jews of the Muslims, or women or men, or the French or the English or the immigrants or the left-handed. It doesn't matter, because from the moment the idea lodged in their fevered minds, it was outside the possibility of reason. This isn't pop psychology. This is simply what we all know to be true, because we all live in the world.

Does the increasingly heated political rhetoric of our times – the personal attacks, the wild distortions, the disintegration of civility that marks the modern dialectic – prompt angry people to act who otherwise might not? Does the anonymous vitriol that spews across the web help dissolve the inhibitions that might otherwise deter them? Do our increasingly polarized and unrestrained media play their part? Do blood-soaked video games cheapen the value of life for some already-damaged minds?

In the days ahead, some people are going to make such claims, but they will never be able to marshal convincing evidence, because such things are beyond accurate measurement. In our hearts, or our guts, we may fear it could be so. But we can't know.

And though we don't intend to, we risk cheapening the real tragedy that confronts us. A human life taken from a family, a community, from all of us, by a senseless act of evil, is made all the more evil because it has no meaning.

There is no way to stop people from trying to draw lessons that should not be drawn from Tuesday night's shooting. The rest of us will follow what we hope is the wiser course. We will simply mourn.