I'm the first one to admit that in the grand scheme, I really don't know anything. But here's the way I see it:
An incident such as just transpired in Paris has several elements to be scrutinized: motivation (such as, say, adherence to a violent ideology), facilitation (such as, say, how the killers were funded and/or armed), and provocation (such as, say, blowback, or retaliation to western foreign policy).
This list is by no means exhaustive; there are likely others, many others, but these are predominantly what I'm seeing discussed around the web.
But there's another, crucial element that I'm not seeing discussed so much, which is that of "enabling". The others I've mentioned above factor into the *launch* of such an attack, but *enabling* is what determines the *success* of the attack, once it is launched.
And what enabled the success of that attack—just as in many of the mass killings here in the US—was the people's ability (and right) to defend themselves being surrendered (forcibly or voluntarily) to the state, which is, in truth, entirely incapable of defending them.
So regardless of the *cause* or *reason* for the attack, the bottom line is, the *success* of the attack is attributed to one thing, and one thing only: a disarmed populace.
So we can debate the rest until we're all blue in the face, but until we establish (or return to) free societies—which would also be, by definition, armed societies—attacks such as these will continue, largely unabated.