Mark Steyn writes:

We’re in danger of missing the forest for the trees. The forest is the ideology. It’s the ideology that determines whether you can find enough young hotshot guys in the neighborhood willing to strap on a suicide belt or (rather more promising as a long-term career) at least grab an AK-47 and shoot up a hotel lobby. Or, if active terrorists are a bit thin on the ground, whether you can count at least on some degree of broader support on the ground. You’re sitting in some distant foreign capital but you’re of a mind to pull off a Mumbai-style operation in, say, Amsterdam or Manchester or Toronto. Where would you start? Easy. You know the radical mosques, and the other ideological front organizations. You’ve already made landfall.

It’s missing the point to get into debates about whether this is the "Deccan Mujahideen" or the ISI or al-Qaida or Lashkar-e-Taiba. That’s a reductive argument. It could be all or none of them. The ideology has been so successfully seeded around the world that nobody needs a memo from corporate HQ to act: There are so many of these subgroups and individuals that they intersect across the planet in a million different ways. It’s not the Cold War, with a small network of deep sleepers being directly controlled by Moscow. There are no membership cards, only an ideology. That’s what has radicalized hitherto moderate Muslim communities from Indonesia to the central Asian ‘stans to Yorkshire, and co-opted what started out as more or less conventional nationalist struggles in the Caucasus and the Balkans into mere tentacles of the global jihad.

And the name of the ideology is Islamism. Or simply Islam. How does Islamism differ from Islam if at all?  

What should we do about it? Inform ourselves about it thoroughly. Examine it critically. Argue against it insistently. Make it as unacceptable to the civilized world as Nazism, which it closely resembles.  

When its ideologues use violence, fight them actively.

Be aware of their encroachment by stealth, and resist, every step of the way, their continual efforts to subvert our system of law and government.