A moral justification for killing in self-defence

In the first part of this paper I will argue that for a case to be one of killing in self-defence at least the following three important conditions need to be met: (i) the defender's death must seem to him/her to be imminent; (ii) there must be a choice forced upon the defender between being killed or killing his/her attacker; (iii) the responsibility for (i) and (ii) must be the attacker's. I go on to point out that a lethal use of force which meets conditions (i)—(iii) is thought by most people to be morally permissible. However we believe also that everyone has the right to life and this cannot be taken away under any circumstances. But if this is so, how can we justify one person intentionally killing another? Or to put the point differently: what, in our moral assessment of such cases, are we to claim an attacker has done that is so morally wrong we are prepared to argue that if one of them has to be killed, it is the attacker? I hope to answer this question in the second part of my paper by developing a strand of ethical thought, associated with Kant.