Every weapons system, from the bow and arrow to the intercontinental ballistic missile, sometimes kills the wrong people. So why has the revelation that a U.S. drone strike accidentally killed two al-Qaida hostages — a U.S. citizen and an Italian aid worker — created such a storm of drone "rethinking"?

Part of the answer is that liberal critics of drone strikes, who've questioned their legality, are using the opportunity to repeat and reframe their criticisms. I've joined in some of that criticism in the past and stand by it.

But the deeper reason for the renewed discussion is a pernicious myth: the fantasy that drones are uniquely precise. From the start, this fantasy of precision has been at the heart of the political and tactical appeal for U.S. President Barack Obama. The same myth has also been central to legal criticisms of the strikes, from the standpoints of U.S. constitutional law and of international law.