First, there’s the practical question of whether killing terrorists in this manner creates new ones. And in Pakistan, for example, the government has responded to public outrage by banning drone flights from an airfield that previously had been an operational hub, according to the Financial Times.

There is also a legal question. The Obama administration asserts that international law clearly permits the targeting of individuals who are planning attacks against the United States. But this standard requires near-perfect intelligence — that we have identified the right target, that we are certain of the target’s nefarious intentions, that the target is inside the house or car that the drone has in its sights. Mistakes are inevitable; accountability is doubtful at best.

Most troubling of all, perhaps, are the moral and philosophical questions. This is a program not of war but of assassination. Clearly, someone like Ayman al-Zawahiri — formerly Osama bin Laden’s second-in-command, now the leader of al-Qaeda — is a legitimate target. But what about others such as the Somali “militants” who may wish to do us harm but have not actually done so? Are we certain that they have the capability of mounting some kind of attack? Absent any overt act, is there a point at which antipathy toward the United States, even hatred, becomes a capital offense?