Necessity is also sensitive to the different probabilities of success of various defensive options. Imagine that in Murder, Victim can either kill Attacker, which has a .9 chance of saving Victim’s life, or break Attacker’s arm, which has a .1 chance of saving Victim’s life. We are likely to think that killing Attacker counts as necessary despite the chance that a much smaller harm could also save Victim’s life. But our intuitions might change as we increase the chances of success of the lesser harm. If breaking Attacker’s arm has a .7 chance of saving Victim’s life, perhaps killing Attacker does not satisfy the necessity constraint.