From my Facebook feed, an email from a French journalist who was held hostage by ISIS.

I am as distressed as anyone about the events in Paris. But I am not shocked or incredulous. I know Islamic State. I spent 10 months as an Isis hostage, and I know for sure that our pain, our grief, our hopes, our lives do not touch them. Theirs is a world apart.

...Even now I sometimes chat with them on social media, and can tell you that much of what you think of them results from their brand of marketing and public relations. They present themselves to the public as superheroes, but away from the camera are a bit pathetic in many ways: street kids drunk on ideology and power. In France we have a saying – stupid and evil. I found them more stupid than evil. That is not to understate the murderous potential of stupidity.

...Everything convinces them that they are on the right path and, specifically, that there is a kind of apocalyptic process under way that will lead to a confrontation between an army of Muslims from all over the world and others, the crusaders, the Romans. They see everything as moving us down that road. Consequently, everything is a blessing from Allah.

With their news and social media interest, they will be noting everything that follows their murderous assault on Paris, and my guess is that right now the chant among them will be "We are winning". They will be heartened by every sign of overreaction, of division, of fear, of racism, of xenophobia; they will be drawn to any examples of ugliness on social media.

Central to their world view is the belief that communities cannot live together with Muslims, and every day their antennae will be tuned towards finding supporting evidence. The pictures from Germany of people welcoming migrants will have been particularly troubling to them. Cohesion, tolerance – it is not what they want to see.

The full letter is worth reading.

I know very little about ISIS, but I am reluctant to write off murderous rebellious groups as stupid, since Westerners have a long history of labeling very cold and calculating enemies as barbarians, and generally underestimating their abilities and ideological appeal. I saw this in northern Uganda with Joseph Kony.

But I am also struck by how many apparently powerful militaries and rebels are disorganized and not very clever, and seem to succeed in spite of themselves. This is especially in stateless areas where there's no real organizations to contend with.

Reader insights welcome.