In Justified Killing, Whitley R. P. Kaufman argues that none of the leading theories adequately explains why it is permissible even to kill an innocent attacker in self-defense, given the basic moral prohibition against killing the innocent. Kaufman suggests that such an explanation can be found in the traditional Doctrine of Double Effect, according to which self-defense is justified because the intention of the defender is to protect himself rather than harm the attacker.