by Tim Harding
Is it justified to kill an innocent threat in defence of oneself or others?
An ‘Innocent Threat’ is a person who poses an imminent threat your life, but who is not the originating cause of that threat, as in the ‘Falling Fat Man’ case hypothesised by Thomson (see below). Some philosophers such Thomson argue that it is morally permissible to kill an Innocent Threat in self-defence (Thomson, 1991); whilst other philosophers such as Otsuka argue that it is not permissible (Otsuka, 1994). In this essay, I intend to argue that it is justified to kill an innocent threat in defence of oneself or others, but on different grounds to those used by Thomson. My grounds are (1) the traditional conditions for justification of self-defence; (2) the Doctrine of Double Effect (which is rejected by Thomson within this context); and (3) utilitarianism, in cases of defending more than one person.
In her 1991 paper on ‘Self-Defense’, Thomson provides three hypothetical cases in which she thinks it is morally permissible for you to kill a person in self-defence (‘Yes cases’); and three cases in which she thinks it is not permissible (‘No cases’). These cases are:
|Yes cases||No cases|
A Villainous Aggressor intends to kill you, as in the case of a truck driver deliberately trying to run you over; whereas an Innocent Aggressor is not to blame for his aggression (for example, if he or she is insane).
An Innocent Threat does not intend to kill you, but will nevertheless do so unless you kill him or her. For example, in Thomson’s Falling Fat Man case, you are lying in the sun on the balcony of your apartment and a fat man pushed by another person is falling towards you. The only way you can prevent him falling on you and killing you is by moving an awning, which will deflect his fall on to the road below, where he will die. If you do not deflect his fall in this way, your body will cushion his fall and he will live (but you will die). The important point is that not only is the Falling Fat Man innocent, but he is not the cause of his fall towards you (Thomson, 1991:287).
Thomson argues that there is no moral difference between the three ‘Yes cases’ – in each case the threat will kill you if you do not kill him or her. She says that, other things being equal, every person Y has a right against X that X not kill Y. In summary, she concludes that the threats in the ‘Yes cases’ will violate your rights that they not kill you, and therefore they lack rights that you not kill them (Thomson, 1991:300-305).
In contrast, bystanders are not threats – they are not causally involved in the imminent threat to your life. Thomson concludes that bystanders do have rights not to be killed and therefore may not be killed in self-defence against a threat not caused by the bystander (Thomson 1991: 298-299).
On the other hand, in his 1994 paper Otsuka argues that there is no moral difference between an Innocent Threat and a bystander. He thinks that it is never justified to kill innocents in self-defence. It is morally impermissible to kill a bystander and therefore it is also impermissible to kill an Innocent Threat.
The implication of Otsuka’s theory that you are morally obliged to lie back and let the Fat Man fall on you is counter-intuitive and likely to be rejected by most people. Appeals to intuition and public opinion are, of course, not philosophical arguments, but I think they can sometimes act as a ‘reality check’ to indicate that there might be something inadequate with a moral theory like Otsuka’s; and that alternative approaches need to be considered.
For a start, Otsuka’s theory conflicts with the Hobbesian account of self-defence that if one will die unless one does X, then one has a right to do X. However, this right needs to be limited in some way.
The traditional conditions for justification of self-defence are that (a) the threat must be imminent; (b) the defensive violence must be necessary; and (c) the force used must be proportionate to the threat. I would argue that conditions (a) and (b) are an intrinsic component of the ‘Falling Fat Man’ case. The proportionality condition (c) is demonstrated in DDE criterion (1) below.
The Doctrine of Double Effect (DDE) states that we may do what will cause a bad outcome in order to cause a good outcome if and only if (1) the good is in appropriate proportion to the bad and (2) we do not intend the bad outcome as our means to the good outcome (Thomson, 1991:292). For example, it is morally permissible to give a terminally ill cancer patient enough morphine to relieve excruciating pain even if we know that this dose will kill the patient. Thomson rejects the application of the DDE to the cases under discussion on the grounds that a person’s intentions are morally irrelevant (Thomson, 1991:293-296).
My view is that intentions are relevant to the morality of killing in general and to the killing of Innocent Threats in particular. For example, in general terms, the essential moral difference (leaving aside the legal difference) between a murder and a manslaughter charge is one of intent. All other facts of the case may be identical.
I think that Innocent Threats meet the criteria for the application of the DDE, as follows:
(1) the good is in appropriate proportion to the bad because either you will be killed or the Innocent Threat will be killed. Either way, one person will die; and
(2) your intent in defending yourself from an Innocent Threat (for example, by shielding yourself from the Falling Fat Man) is merely to save your own life. The death of the Falling Fat Man is an unavoidable consequence of the necessary action you take to save your life, rather than the purpose of your action.
The DDE can also apply to the defence of others – the above criteria could also be met in such cases. In cases where more than one person is being defended, the good may even outweigh the bad.
Utilitarianism is of little assistance in the Falling Fat Man case. Both you and the fat man are likely to have a preference to live. Either way, one person will die. The life of one of you may be more valuable to the community than the other and therefore have better consequences from being saved, but that is an assessment you are unable to make when a fat man is about to fall on you! However, in other cases Utilitarianism may be relevant to the defence of more than one other person, on the grounds that saving more than one life would be a better consequence than saving only one life.
In conclusion, I think it is justified to kill an Innocent Threat in defence of oneself or others on the grounds of the traditional conditions for self-defence; the Doctrine of Double Effect; and utilitarianism in cases of defending more than one person.
Otsuka, M. (1994) ‘Killing the Innocent in Self-Defense’ Philosophy and Public Affairs, Vol. 23, No. 1 (Winter, 1994), pp. 74-94.
Thomson, J. (1991) ‘Self-Defense’ Philosophy and Public Affairs, Vol. 20, No. 4 (Autumn, 1991), pp. 283-310.
 Otsuka also argues that it is morally impermissible to kill an Innocent Aggressor, but that issue is outside the scope of this essay topic.
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