Suppose Bob paid professional killer Alice to kill him on a day of her choice in the next month. Next day, Bob changes his mind, but has no way of contacting Alice. A week later, Bob sees Alice in the distance aiming a rifle at him. Is it permissible for him to shoot Alice in self-defense?
I take it (somewhat controversially) that killing a juridically innocent person is murder even if the victim consents. Thus, Alice is attempting murder, and normally it is permissible to shoot someone who is trying to murder one. But it seems rather dastardly for Bob to shoot Alice in this case.
On the other hand, though, if Bob hired Alice to kill Carl, and then repented, shooting Alice when Alice is trying to murder Carl does seem the right thing for Bob to do if there is no other way to save Carl’s life.
What is the exact moral difference between the two cases? In both cases, Alice is trying to commit a murder, and in both cases Bob bears a responsibility for this.
I think the difference has something with duties of restitution. When one has done something wrong, and then repented, one needs to do one’s best to “undo” the wrong, repaying the victims in a reasonable manner. But there is a gradation of priority, and in particular even if one is oneself among the victims (Socrates thinks the wrongdoer is the chief victim, since in doing wrong one damages one’s virtue), restitution to others takes priority. In both cases, Bob has harmed Alice by tempting her to commit murder. In the case where Alice was hired to murder Bob, restitution to Alice takes precedence over restitution to Bob, and refraining from killing Alice in self-defense seems a precisely appropriate form of restitution. In the case where Alice was hired to murder Carl, however, restitution to Carl takes precedence, and Bob owes it to Carl to shoot Alice.
In fact, I suspect that in the case where Bob hired Alice to kill Carl, if the only way to save Carl’s life is for Bob to leap into the line of fire and die protecting Carl, other things being equal that would be Bob’s duty. Normally to sacrifice one’s life to save another is supererogatory, but not so when the danger to the other comes from one’s own murderous intent.
The morality of restitution is difficult and complex.
