By Patrick Appel
Jeffrey Goldberg recently sat down with Daniel Benjamin to talk about al Queda. Benjamin's response to a question about experts who believe there is a 50 percent chance an American city will be attacked with a nuclear device sometime in the next ten years:

I don't think the chance is anywhere near that high, but an attack with an improvised nuclear device is plausible. When you interviewed Michael Chertoff in Aspen, he said he thought that threat would be real in a couple years, right?  I ran a study a few years ago that brought together nuclear weaponeers and terrorism experts, and the conclusion, in essence, was that if al Qaeda could get the fissile material - the hardest part of the process, but by no means impossible - they would likely be able to build a weapon.  I'd put the likelihood of that happening at a small fraction of the 50 percent you cite, but the impact would be so devastating that we need to allocate lots of resources and effort to ensuring that doesn't happen. 

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.