Thomas Nagel at the London Review of Books:
Pacifists are rare. Most people believe that lethal violence may be used in self-defence, or the defence of others, against potentially lethal threats. Military action is justified by a collective institutional version of this basic human right, which sets an outer limit on the right to life. Lethal aggressors who cannot be stopped by lesser means are liable to lethal attack, and this does not violate their right to life so long as they remain a threat. Killing in self-defence is distinct from execution, the killing of someone who is no longer a threat as a punishment for past conduct. It is also usually distinct from assassination, which can be carried out for a wide range of reasons: revenge, political or religious hatred, nationalistic passion and so forth – though occasionally someone who is a lethal threat to the assassin or his community may be targeted.
The development of drone warfare has put these distinctions under strain, and that helps to explain the visceral reaction many people have against it, in spite of its being much less destructive than more traditional forms of military violence. Drones, or UAVs (unmanned aerial vehicles), are more selective in the killing of enemies, produce less collateral damage to non-combatants and impose no physical risk to those who pilot them, since they are sitting in a control station thousands of miles away. Who could ask for more?