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An Eye for an Eye: Proportionality and Surveillance


It is often claimed that surveillance should be proportionate, but it is rarely made clear exactly what proportionate surveillance would look like beyond an intuitive sense of an act being excessive. I argue that surveillance should indeed be proportionate and draw on Thomas Hurka’s work on proportionality in war to inform the debate on surveillance. After distinguishing between the proportionality of surveillance per se, and surveillance as a particular act, I deal with objections to using proportionality as a legitimate ethical measure. From there I argue that only certain benefits and harms should be counted in any determination of proportionality. Finally I look at how context can affect the proportionality of a particular method of surveillance. In conclusion, I hold that proportionality is not only a morally relevant criterion by which to assess surveillance, but that it is a necessary criterion. Furthermore, while granting that it is difficult to assess, that difficulty should not prevent our trying to do so.

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  1. I have argued elsewhere for the applicability of the just war tradition to the ethics of surveillance (Macnish 2014). This paper involves a development of one aspect of that argument. In addition, I am grateful to comments by Thomas Hurka and an anonymous reviewer for improvements made to this paper.

  2. Imagine a farmer extending his field across an international border. As a result the state into which he has encroached declares war on his state. All other things being equal, this declaration would be a disproportionate response.

  3. I am grateful to Thomas Hurka for clarifying this distinction.

  4. I am grateful to Thomas Hurka for pointing this out.


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Correspondence to Kevin Macnish.

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Macnish, K. An Eye for an Eye: Proportionality and Surveillance. Ethic Theory Moral Prac 18, 529–548 (2015).

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  • Surveillance
  • Proportionality
  • Thomas Hurka
  • Just war
  • Datong
  • Oliver O’Donovan