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Responsibility and Self-Defense: Can We Have It All?

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The role of responsibility in our common-sense morality of self-defense is complex. According to common-sense morality, one can sometimes use substantial, even deadly, force against people who are only minimally responsible for posing a threat to us. The role of responsibility in self-defense is thus limited. However, responsibility is still sometimes relevant. It sometime affects how much force you can use against a threatener: less if they are less responsible and more if they are more responsible. Is there a well-motivated theory that can explain both why the role of responsibility is limited and why it is sometimes relevant? It is hard to see what theory could unify these disparate elements of our common-sense morality, and if one cannot be found then we may simply have to revise some of our pre-theoretic beliefs. But it would be an important advantage of a theory if it could justify those beliefs. I will argue that there is a theory of this kind: surprisingly, the familiar rights theory of self-defense, defended by Judith Thomson, can do so if it is suitably supplemented. Along the way I will survey some alternative theories of self-defense and show why they are not up to the task.

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  1. I draw heavily on Thomson throughout and attempt to show that her view of self-defense is best understood in light of her broader theory of rights.

  2. For instance, Quong (2009).

  3. I realize that ‘threatener’ may be a neologism, but ‘attacker’ is too narrow, for reasons that will become clear.

  4. There are in fact a range of ways in which necessary defensive action might involve a response that harms the threatener, including action to block the threat, action to incapacitate the threatener, and so on. For ease, I am going to speak, as McMahan and others do, of liability to harm, but it should be assumed that the harm is being inflicted for one of these specific purposes.

  5. McMahan (2005), for instance, presents the various major theories of self-defense as in agreement that you can kill in self-defensive when and because attackers are liable to defensive action.

  6. I am focusing on the claim that it is permissible to use defensive force. Kantians might defend a stronger claim that it is obligatory to use defensive force, perhaps out of a duty to respect one’s own autonomy. I set this approach aside for present purposes, since it conflicts with the intuitive view that defending yourself is optional and because accepting it would require adopting a broader Kantian theory that I cannot fully consider here.

  7. I am going to assume that infringing someone’s rights is equivalent to wronging him, though the more basic notion, I think, is that of wronging. And I here use the word ‘infringe’ so that it covers all species of wrongings, including those that are (all things considered) permissible and (all things considered) impermissible. There are various different ways of using the term in the literature, but this usage will make my presentation easier. I believe this formulation of the rights theory is the strongest and I defend it in Hosein (2014).

  8. This is mostly an elaboration of Thomson (1991, fn. 13).

  9. Thomson does not quite put it like this, but much of the force of her article comes from this challenge.

  10. The Driver and Cell Phone examples are adapted from those in McMahan (2011, pp. 164–165), while Falling Person is a variant on his case in (McMahan 2009).

  11. There is, of course, a large literature by now on the relation between rights and intention, responsibility, culpability, and so on. I can not fully survey that literature here, but for our purposes it will be enough to see that Thomson’s views on rights are at least one plausible option. I aim to show that with them on hand we can account fully for the role of responsibility in self-defense. This constitutes further evidence for her views about rights. For further discussion about intentions, permissibility, and so on, see, for instance, Scanlon (2008).

  12. Also note that McMahan himself, whose account provides the clearest contrast with Thomson, seems to accept that there is a basic right not to be harmed (a right not tied to the threatener’s responsibility). For according to his account you can only defend yourself against a threatener who is responsible for an unjust threat. And someone creates an unjust threat of harm just in case they would wrong you (or, equivalently, violate your rights) by inflicting that harm on you.

  13. Intuitions elaborated on in Thomson (1992).

  14. Though there may be some temptation to demand a little less compensation from someone who has a good excuse for wrongdoing and would be very heavily burdened by having to provide the full amount of compensation demanded of a fully responsible wrongdoer: in so far as this is so, the account I will offer below explains why.

  15. For a very helpful summary of the literature on the rights theory and cases where a threat lacks agency, see Doggett (2011).

  16. As claimed by, for instance, Otsuka (1994).

  17. See Kamm (1992, p. 48) for similar examples involving people’s bodies, though I find intuitions are especially clear about the car case described.

  18. Someone might say that still you exercised agency in buying the car and parking it your drive and thus accepted all potential liability risks associated with it. I think if we say that we might as well also say that when you walk outside you assume some risk of falling on someone at the bottom of a well due to freak weather.

  19. I borrow the identification point from Victor Tadros’ (2011, p. 55) very similar argument: ‘It is the fact that I am responsible for what my body does, even when it is not a product of my agency, that gives rise to the permission to harm innocent attackers and innocent threats. And I bear that responsibility because my body is me’. Tadros goes on to argue that to fully explain why it is permissible to kill the falling person one needs to appeal to an additional lesser evil justification. I set this aside, since adding this justification is compatible with everything else I have to say.

  20. Some people would find it surprising if one could use force in Cell Phone but not Falling Person, since according to common-sense morality you can kill in both and the attackers appear to be morally indistinguishable, given their similar innocence, lack of responsibility, and likelihood of causing harm. But these cases should only be treated differently on the rights theory if the exercise of agency is essential to rights infringement. And the person who is adamant that rights infringement requires agency has a strong reason to think that there is in fact an important morally relevant difference between the two cases—only one involves the exercise of agency—and thus should not be surprised if the two cases call for very different responses on the part of the victim.

  21. I borrow these examples from Jeff McMahan (2011, Chapt. 4.1.1), who uses them to make the same point about proportionality.

  22. An alternative explanation of these intuitions is that more responsible attackers are generally more determined and thus more difficult to repel. Thus, rather than appealing to proportionality we might appeal to necessity to explain our intuitions: we might say that greater force may typically be used against more responsible attackers because greater force is typically necessary. This suggestion deserves much more extensive treatment than I can pursue here. Very briefly, I think there are some strong intuitions that cannot be explained by this account. For instance, it seems that one can use greater force to stop the culpable person in Clear Mind than to stop a person who has been hypnotized to act in the same way, even though the latter will be just as a determined until the hypnosis wears off.

  23. As discussed in McMahan (2005, pp. 394–395).

  24. McMahan (2011, Chapts. 4.1–4.2) essentially acknowledges this problem.

  25. For instance, they might say that even if it would be fair for the innocent victim to share half the harm with an innocent threatener or bystander, a prohibition on doing harm bars the victim from shifting harm to either of these others in the name of fairness. But then it would be very unclear why this prohibition does not also trump the slight increase in fairness of shifting lethal harm from an innocent victim to a minimally responsible threatener.

  26. As Thomson (1986, pp. 68–71).

  27. Thomson (1971, pp. 62–63) marks this difference by distinguishing between ‘Good Samaritanism’ and ‘Minimally Decent Samaritanism’.

  28. See Thomson’s discussion in The Realm of Rights, p. 122, though note that her terminology is different from mine.


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For helpful comments, I am very grateful to Tyler Doggett, David Mapel, Jeff McMahan, and two anonymous referees.

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Correspondence to Adam Hosein.

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Hosein, A. Responsibility and Self-Defense: Can We Have It All?. Res Publica 23, 367–385 (2017).

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