When, if ever, is it morally permissible to kill in self defence?

When, if ever, is it morally permissible to kill somebody in self defence?

Abstract
This paper will discuss if, and when, it is morally permissible to kill in self defence, and, in order to support my views, I will use ‘thought experiments’ from other philosophers such as Thomson, who puts across scenarios where there is an aggressor or a threat against your life (these titles will be clarified later). I will also use my own analogies, which puts you in a car facing different situations that will kill somebody in order to save another, and the ethics involved in these killings. The first of these situations is called the Non-instinctive Approach, where, when the scenario is posed, the natural reaction is to disagree. The second is the Do-Nothing Approach, where no action is taken to change the circumstances. The third is called Replacement, where bystanders replace you in the situation. Finally, there is Basic defence Approach, when you take out the threat against your life by killing those who threaten/aggressor against you. I will consider criticisms of both mine and other theories and consider any alternatives to both. Through comparing analogies of my own in contrast to the work of others, it will express my views on what makes killing morally permissible or impermissible.

A pre-existent theory
It is a common example among philosophers, where, to defend their points on killing in self defence, the role of those endangering your life are given a name; the name for these people are Villainous Aggressor, Innocent Aggressor and Innocent Threat:
Villainous Aggressor: ‘You are standing in a meadow, innocently minding your own business, and a truck suddenly heads towards you. You try to sidestep the truck, but it turns as you turn. Now you can see the driver: he is a man you know has long hated you... You cannot outrun the truck. Fortunately, this is not pure nightmare: you just happen to have an antitank gun with you, and can blow up the truck. Of course, if you do this you will kill the driver’ (Thomson, 1991:283)
Innocent Aggressor: ‘You are standing in a meadow, innocently minding your own business, and a truck suddenly heads towards you. You try to sidestep the truck, but it turns as you turn. Now you can see the driver: he is a man you know has long hated you, but has also taken some mind altering drugs, that causes him to act differently, so him killing you is not his intention...you can blow up the truck, if you do this you will kill the driver’ (Thomson, 1991:283)
Innocent Threat: ‘You are standing in a minefield, innocently minding your own business and waiting for the rescue team, who should be soon arriving, when you see a man in a truck heading towards you, although not at you. He gets close enough that, if he touches a mine, it will kill you but, being in a car, he will only be injured. You cannot run because you know you are surrounded by mines. However, you do have an antitank gun, which can blow up the truck, thus killing the driving.
In Villainous Aggressor, it is believed to be morally permissible to blow up the truck and kill the driver. There are only two options available in this scenario; do nothing and die or act, kill the driver and live. Because the driver has the intention to kill you and there are no other options, you are morally allowed to shoot the truck, as, like Thomson argues, everybody has the right to life, so should not be killed. But the driver ‘will otherwise violate your rights that they not kill you, and therefore lack rights that you not kill them’ (Thomson, 1991:302). Simply, in threatening your life, the driver loses the right to not be killed themselves.
Thomson argues that killing Innocent Aggressor is also morally permissible. Unlike Villainous Aggressor, Innocent Aggressor does not have the same type of intention; although they have long hated you, they, through no conscious choice of the own, are aggressing against you. Thus, Thomson adopts the Irrelevance-of-Intention-to-Permissibility Thesis, which says the intention of an agent is irrelevant as sometimes the actions and consequences are exactly the same and so are both morally permissible/impermissible. But if the intention differs, and intention has an effect on permissibility, then they would not be the same, therefore intention cannot be significant given that it has previously been stated that the actions, consequences and permissibility are the same. Thus the main point from Villainous Aggressor (that your life is under threat) can be carried through to Innocent Aggressor as they are positioned in such a way that your life is threatened, and when your life is under threat, those who threaten it lose the right to not be killed and it’s morally permissible to kill them.
Similar views are also applied to Innocent Threat; the fact that the Threat is ‘innocent’ is irrelevant, so it’s important to look at why Thomson believes it is also morally permissible to kill the Innocent Threat, given they aren’t actually aggressing against you. For example, if a woman was pregnant and having the child would kill her, it can be seen that ‘no person is morally required to make large sacrifices to sustain the life of another’ (Thomson, 1971;9) i.e. the mother doesn’t have to die and it is morally justifiable to continue with an abortion. In Innocent Threat, the driver is a danger to your life, and there is nothing to say that you have to die in order for him to live, and, like the other examples, the threat to your life gives you moral permissibility to kill him; this is Thomson’s view on morally permissibility in killing in self defence.
I believe that it is morally impermissible to kill in self defence under all circumstances, given that all life is sacred, so I oppose with the reasoning Thomson gives.

Criticisms of this theory
The issues that I see with these theories are that it is never morally permissible to kill, but rather it is justifiable with ideas of morality interwoven. In villainous aggressor, the driver has intent and holds a threat against you, but through the reasoning of Thomson, it says that you are morally permissible to kill him because he threatens your life; in doing so he loses the right to life and you gain the right to defend yourself and to kill him. However, although the truck driver is morally “inferior” to you because he threatens your life, it does not excuse you killing him; I believe everybody has every right to defend themselves, but not when it results in death (you causing harm upon someone else). When under attack/threat, a person gains the right to defence, but not the right to kill, so in defending yourself through attacking, knowing he’ll die, you become an aggressor, which would then given him the right to kill you in self defence, so this argument is invalid as there is no end to the cycle. You can justify killing the aggressor; you are acting in self defence, ‘human beings have a right to life and therefore a right to protect themselves’ (Leverick, 2006:44), but the feeling of self-worth and preservation doesn’t make it morally permissible to kill, because otherwise you would be able to kill in self defence under every circumstance and it still be considered morally permissible. The same applies to innocent aggressor and innocent threat, but when considering killing them, people are more inclined to be less resolved about it, due to the “lack of intent” from the innocent aggressor and innocent threat, given they cannot control their actions against the victim.

Alternative theory to pre-existent theory
Thus I have come up with my own theory that holds within it 4 different scenarios, the theory being this: You have gone out with a friend in the evening and they are driving you home in their car. It is very dark and your headlights, through no fault of your own, aren’t working. As you approach an intersection, your friend notices a lorry traveling at high speeds that, if undeterred, will hit your car and kill you both (remember he cannot see you because you have broken headlights). Your friend completely freezes in fear and there is nothing you can do to move them. Your options are as such:
(1) Non-Instinctive Approach: Kill your friend in order to divert your car. The only person to die in this case is the friend, whom you killed.
(2) Do-Nothing Approach: Don’t take any course of action to change the event. You let you and your friend die.
(3) Replacement: Turn into a car next to you so that they and they alone hit the truck. The occupant of the vehicle dies, but allows you and your friend to live.
(4) Basic defence Approach: Shoot the driver of the truck, causing his truck to divert so that you and your friend live.
Although I believe it is justifiable to defend yourself, it does not make it morally permissible to defend yourself through killing someone else, therefore I believe, if it is not possible to take a course of action that does not result in you killing someone, people should choose to do nothing and, although may be considered suicide, it is morally permissible to do so, whereas the other courses of action are not.

Criticisms of my alternative theory
Undeniably, you are responsible for your life as well as your friends once you are the only one capable of making decisions, so you should feel at least inclined to act in order to protect what you are responsible for, and it is morally permissible to do so. It is difficult to argue (1) is morally permissible as the driver was originally responsible for you and their own actions may result in your death, so it is, at least, justifiable to kill them, even though they are your friend and aren’t the actual threat (the truck) but their actions have put your life under threat, so it is morally permissible to kill them. In similar circumstances to Bystander, (3) is morally impermissible, but consider factors like the ratio of passengers in the other car to the two you’re responsible for; it is morally permissible to turn a Trolley onto one in order to save five, otherwise it ‘violates a positive duty to save five lives’ (Thomson, 1976:206) so it is also morally permissible to turn into the neighboring car, given that there is only 1 passenger. Now I argue (4) is morally permissible, given, although an Innocent Threat, they hold a threat to the lives you are responsible for. When giving an analogy about a fat man falling off a cliff towards you; options are either a) crush you to death but he’ll be fine or b) shift your awning, deflect the fat man onto the road, where he will die, but you live. Thomson points out that he ‘is not doing anything at all – he is merely falling towards you’ (Thomson, 1991; 289), but ‘in all three cases [Villainous Aggressor, Innocent Aggressor and Innocent Threat], the person you kill if you proceed will otherwise kill you’ (Thomson, 1991;289) and in doing so lose the right to life them self, thus you can shoot the driver.

Defence to criticisms of my alternative theory
Morals can be defined as what is acceptable to someone, but I believe, no matter what situation, it is always morally impermissible to kill someone. I believe everybody is morally obligated to not kill, including killing in self defence. You cannot control the actions and events that carry out in life, so if someone tries to kill you or threatens your life, although it can be justified to kill in self defence, you are obligated not to. There’s also a significant difference in defending yourself with someone dying as a result and defending yourself, knowing someone will die as a result of your defence, because this knowledge makes you an aggressor and arguably just as morally wrong as the initial aggressor/threat, thus it cannot be said killing in self defence is morally permissible because it is morally impermissible to be an aggressor, even against an aggressor/threat.
Under no circumstances is it morally permissible to kill someone, including in self defence. Thomson looks at whether killing is worse then letting die when both result in death; ‘Alfred hates his wife and wants her dead. He puts cleaning fluid in her coffee, thereby killing her’, whereas ‘Bert hates his wife and wants her dead. She puts cleaning fluid in her coffee (being muddled, thinking it’s a cream). Bert happened to have the antidote to cleaning fluid, but he does not give it to her, but lets her die.’ (Thomson, 1976; 204). To me, although Alfred took the steps to kill his wife, both are morally wrong, so both can be considered as bad as each other. The same applies to killing someone. Killing someone may be worse than killing someone in self defence but both are morally wrong-killing is, no matter what, killing-so killing is always morally impermissible, even in self defence.

Bibliography
Leverick, Fiona. 2006, Killing in Self-Defence. Oxford University Press.
Thomson, Judith Jarvis. 1971, ‘A Defence of Abortion’. Philosophy & Public Affairs, Vol. 1, No. 1 (Autumn, 1971), pp. 9
Thomson, Judith Jarvis. 1976, ‘Killing, Letting Die, and the Trolley Problem’. Monist, 59:2, (April, 1976), pp. 204-206
Thomson, Judith Jarvis. 1991, ‘Self Defence’. Philosophy and Public Affairs, Vol.20, No.4, (Autumn, 1991), pp. 283-302

Bibliography: Leverick, Fiona. 2006, Killing in Self-Defence. Oxford University Press. Thomson, Judith Jarvis. 1971, ‘A Defence of Abortion’. Philosophy & Public Affairs, Vol. 1, No. 1 (Autumn, 1971), pp. 9 Thomson, Judith Jarvis. 1976, ‘Killing, Letting Die, and the Trolley Problem’. Monist, 59:2, (April, 1976), pp. 204-206 Thomson, Judith Jarvis. 1991, ‘Self Defence’. Philosophy and Public Affairs, Vol.20, No.4, (Autumn, 1991), pp. 283-302