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Robots as “Evil Means”? A Rejoinder to Jenkins and Purves

Published online by Cambridge University Press:  12 September 2016


The notion that some means of waging war are mala in se is a confronting one. Surely, any weapon can be used for good or ill? Philosophers often try to justify the category of mala in se by suggesting that some weapons are inherently incapable of being used in accordance with the just war principles of distinction and proportionality. This line of argument faces two obvious objections. First, claims about the limits of particular weapons typically fail to consider the different contexts in which they might be used. For example, anti-personnel mines can be used as defensive measures for fixed installations in marked locations that are fenced off from civilian intrusion. Second, deriving the category of mala in se from the principles of distinction and proportionality makes it redundant. The argument that some weapons cause disproportionate suffering is more persuasive, but it falters if one conducts an honest appraisal of the nature and extent of the suffering caused by weapons that are not held to be mala in se.

Copyright © Carnegie Council for Ethics in International Affairs 2016 

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1 Sparrow, Robert, “Robots and Respect: Assessing the Case against Autonomous Weapon Systems,” Ethics & International Affairs 30, no. 1 (2016), pp. 93116 CrossRefGoogle Scholar.

2 Sparrow, Robert, “Killer Robots,” Journal of Applied Philosophy 24, no. 1 (2007)CrossRefGoogle Scholar; Heather M. Roff, “Killing in War: Responsibility, Liability, and Lethal Autonomous Robots,” in Fritz Allhoff, Nicholas G Evans, and Adam Henschke, eds., Routledge Handbook of Ethics and War: Just War Theory in the Twenty-First Century (Milton Park, Oxon: Routledge, 2013).

3 This is undoubtedly to overstate the case: only the most hardline of deontologists would claim that there were things that we should not do no matter how many lives were at stake. Equally well, however, anyone who thinks that we should be willing to use any sort of weapon once doing so will bring about a good result doesn't really believe in the category of mala in se. A more precise formulation might therefore be that if a weapon is malum in se, its use will be a moral tragedy even if it saves lives.

4 Sparrow, Robert, “Predators or Plowshares? Arms Control of Robotic Weapons,” IEEE Technology and Society 28, no. 1 (2009)CrossRefGoogle Scholar; Robert Sparrow, “Robotic Weapons and the Future of War,” in Jessica Wolfendale and Paolo Tripodi, eds., New Wars and New Soldiers: Military Ethics in the Contemporary World (Surrey, U.K.: Ashgate, 2011). See also Mark Gubrud, “Why Should We Ban Autonomous Weapons? To Survive,” IEEE Spectrum, June 1, 2016,

5 There is, no doubt, a real danger that they will be developed and deployed even if such a prohibition is enacted.