Is Osama bin-Laden Dead?

There are three key words missing from this news report about a new Al-Qaeda videotape: Osama bin Laden. He is generally assumed to be alive but doesn’t it seem fairly likely that he may already be dead? If he can’t be found in order to be captured or killed, how are we to know that he’s still alive? But here’s the question I really want to know the answer to: assuming that Bin Laden has died, whether from natural causes or otherwise, how long would it take the U.S. even know it? Would his disciples be capable — and desirous — of keeping his death a secret in order to maintain his mythic status?