A terrorist captured alive is a major plus for investigators and counterterrorism efforts -- and for the families and victims who may now see some justice. The question now is: Will he talk? It would be a promising turn of events if he did, but the capture would still be a success if he doesn't.
Since European interrogators are not under the same time constraints as in the United States, they will be able to spend considerable time with Abdeslam to get him to talk. Traditional interrogation techniques are often successful in getting detainees to feel the urge to disclose information.
It may not work. But here's a plus most are not thinking of: His terrorist brethren likely will not know whether it does work. Even if Abdeslam never utters a word again, they will have no idea that is the case. They do not know if Abdeslam, who kept running and hiding rather than sacrificing his own life for a cause that he seemed more than willing to have others sacrifice theirs for, will be weak or strong in the face of his upcoming isolation and interrogation.
Given the nature of terrorist organizations and the compartmentalization of information, these other ISIS members may not know who and what else Abdeslam knows. In other words, those in both his inner and outer circles will simply have no sense of how much Abdeslam will try to save himself and sacrifice them.
And this fact alone gives European officials exceptional leverage. Any effective law enforcement agency will start to purposefully "leak" information to the media that Abdeslam is spilling his guts, making amends, chatting away and looking for a deal.
It may or may not be true; for all we know, Abdeslam might not be speaking at all. But his terrorist colleagues will have to wonder if Abdeslam, who never did use that suicide vest he was supposed to detonate during the Paris attacks or anytime after, is a weak person to depend on.
It is this growing sense of unease by ISIS members that will help counterterrorism officials. If you are one of the likely dozens of ISIS members who helped him along the way -- helped hide him, feed him, protect him -- or aided him in the Paris attacks, you have got to be thinking that this isn't such a good turn of events. And so you run. Or you do something stupid. Or you turn on each other.
In the Cold War days, the technique of using intelligence to sow seeds of distrust and fear among an enemy group was called "black propaganda." It hasn't gone away. And the hope is that these terrorists, in response to Abdeslam's capture, will worry so much that they will stray from their plans, move and transit in ways that they hadn't once intended, and therefore make themselves vulnerable to detection and capture. As a result, more terrorists will be caught.
Some will talk and some will not, but each capture will provide more information, helping investigators put together a clearer picture of the web of networks.
Will Abdeslam talk? If he does, we will learn a lot about the ISIS organization in Europe. If he doesn't, we still could.