We can say they are evil people doing evil things for evil ends. Or we can do the hard work of understanding the context that made them, so that we can create a context that unmakes them.

We can analyze the ways its violent tactics are effective for its purposes given the local power dynamics, so that we can also better understand its weak spots. And we can ask how it is that normal men — men who were not born evil — get turned into monsters, so that we can work to change the structures that produce terrorists over the long term instead of locking ourselves into an endlessly repeated, short-term policy of “killing fanatics” until they are gone.

Trying to understand something isn’t the same as trying to justify or excuse it. That’s a basic mistake, and a costly one.

As Jane Harman, president of the Woodrow International Center for Scholars, recently wrote: “We can’t counter radical narratives if we don’t understand the motives of the radicalized.”