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The Doctrine of Double Effect and the Trolley Problem

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  1. See Bruers and Brackman, “A Review and Systematization of the Trolley Problem,” Philosophia 42:2 (June 2014): 251–269; T. Scanlon, Moral Dimensions: Permissibility, Meaning, Blame (Cambridge, MA: Harvard University Press, 2008); Peter Singer, “Ethics and Intuitions,” Journal of Ethics 9:314 (2005): 331–352, p. 340; Matthew Liao, “The Loop Case and Kamm’s Doctrine of Triple Effect,” Philosophical Studies 146:2 (2009): 223–231; H. Sauer, “Morally Irrelevant Factors: What’s Left of the Dual Process Model of Moral Cognition?,” Philosophical Psychology 25:6 (2012): 783–811, p. 797. Frances Kamm suggests the DDE can be saved from the objection, but only by radically revising it into a doctrine of “Triple Effect” (Intricate Ethics: Rights, Responsibilities, and Permissible Harm (New York: Oxford University Press, 2007)); I take it that this position concurs with the consensus that the Loop problem refutes the DDE.

    It should be noted that Thomson’s original article on the subject does not actually discuss the DDE, but instead focuses on the Kantian idea that one may not treat people as a means (J.J. Thomson, “The Trolley Problem,” Yale Law Journal 94 (1985): 1395–1415 (reprinted in Rights Restitution and Risk (Cambridge, MA: Harvard University Press, 1986)). However, the Loop variant raises the same problem for the DDE’s focus on intention, and it has become standard in the literature to treat Thomson’s argument as if it is directed against the DDE (see e.g. Liao 2008). It is my view that the Kantian position is in practice identical to the idea developed in the DDE (a view I defend in Justified Killing: The Paradox of Self-Defense (Maryland: Lexington Books, 2009)).

  2. Joshua Greene, Moral Tribes (New York: Penguin, 2013), p. 230. Though his intended meaning is clear, in fact Greene has confused his metaphors. A “showstopper” is a term from the theater, referring to a musical number so well received that the audience’s wild applause temporarily stops the performance. Thus a showstopper indicates a smashing success, not a failure.

  3. Liao, Wiegmann, Alexander, and Vong, “Putting the Trolley in Order: Experimental Philosophy and the Loop Case,” Philosophical Psychology 25:5 (2012): 661–671.

  4. Jeff McMahan, “Intention, Permissibility, Terrorism, and War,” Philosophical Perspectives 23 (2009): 345–372, p. 345.

  5. Kaufman 2009, op. cit.

  6. This is a highly simplified version of the DDE sufficient for purposes of this essay; a full account of the DDE is provided in Kaufman 2009, op. cit.

  7. Marc Hauser, Moral Minds (New York: Harper Perennial, 2008), p. 128. The use of Marc Hauser’s research data of course raises the problem of its reliability given his removal from Harvard in 2011 based on scientific misconduct. However, the alleged misconduct seems to have been limited to Hauser’s studies on monkeys and animal cognition and Hauser’s questionable interpretation of monkey behavior. There is no evidence of which I am aware that it extends to the evidence collected from online surveys of peoples’ responses to the trolley problems, which does not involve similar problems of interpretation. The online Moral Sense Test is still active, being run by other members of the Psychology Department at Harvard. Cf. also Edmonds 2014 p. 200: “there has been no suggestion that there was anything untoward about the published results” in the area of trolley problems.

  8. I assume here an act-utilitarian theory (seemy Honor and Revenge: A Theory of Punishment (New York: Springer, 2012) pp. 81–82 for a discussion of the problems with rule-utilitarian theories).

  9. Hauser, op. cit.

  10. Thomson, op. cit., p. 102.

  11. Singer, op. cit., p. 340.

  12. Scanlon, op. cit., p. 18.

  13. Two new books have recently appeared as accounts of the trolley problem for a popular audience: David Edmonds, Would You Kill the Fat Man?, and Thomas Cathcart, The Trolley Problem: or Would You Throw the Fat Guy Off the Bridge?.

  14. Cass Sunstein, “Moral Heuristics,” Behavioral and Brain Sciences 28 (2005): 531–573, p. 541.

  15. Kaufman2009, op.cit.

  16. Otsuka for example notes that, unlike many other examples used in ethics, “looping cases are not modelled on any real-world cases with which we are familiar” (M. Otsuka, “Double Effect, Triple Effect and the Trolley Problem,” Utilitas 20:01 (2008): 92–110, p. 109). Of course, Trolley and Fat Man are also somewhat artificial, even if less so than the Loop case.

  17. Additionally, since Thomson does not say how large this loop is, one might reason that one would have cause to switch the trolley even if the fat man were not present, just because it buys time to try to get the five people off the track. If so, one is not intending the death of the fat man, or so one could argue.

  18. Liao et alia 2012, op. cit., p. 229.

  19. Hauser, op. cit., p. 128. Hauser uses a slightly modified version of the Loop case, but there is no reason to believe that it changes the case in any important respect.

    It is not clear who Singer is referring to when he says “most people,” nor does he provide any evidence to back up his assertion. It is notable however that an online poll of philosophers gave very different results from the Hauser poll: 67% of philosophers said that it is permissible to redirect the trolley in the Loop case (though the sample size is small: only 76 participants) ( Otsuka plausibly suggests that philosophers’ intuitions may be biased by the powerful influence of Thomson’s initial article (op. cit., 2008, p. 109). We might also speculate that the widespread hostility to the DDE may have influenced philosophers into accepting her conclusion in the Loop case.

  20. Op. cit., p. 102.

  21. Note that Thomson actually writes that the extra feet of track can make no “major” moral difference. It is unclear what this qualification is supposed to mean.

  22. Thomson, op. cit., p. 102.

  23. Liao, op. cit.

  24. McMahan, op. cit., p. 359.

  25. He also does not explain the qualification “virtually” indistinguishable.

  26. Otsuka 2008, op. cit., p. 110.

  27. Ibid., pp. 108–109.

  28. Scanlon, op. cit.

  29. Greene 2013, op. cit., p. 231, makes a similar argument.

  30. McMahan raises the question as to whether, once one has switched the trolley, one is morally required to try to get the Fat Man out of the way (op. cit. 2009, p. 359). If one passed up on an easy opportunity to save him, it seems to me that McMahan is correct that one is now acting morally impermissibly. But it does not seem to me that this entails that one is acting impermissibly in the more likely scenario, that there is no easy way to get the Fat Man to move away from the train.

  31. One might see Kamm’s attempt to draw even more subtle distinctions in the nature of intention as another way of suggesting that the case does not clearly fall under either side of the dichotomy, intended versus foreseen (Kamm, op. cit.).

  32. Op. cit., p. 255.

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Kaufman, W.R.P. The Doctrine of Double Effect and the Trolley Problem. J Value Inquiry 50, 21–31 (2016).

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  • Causal Chain
  • Standard Case
  • Loop Variant
  • Moral Intuition
  • Double Effect