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Comparing Harms: The Lesser-Evil Defense and the Trolley Problem

  • Robert Hallborg (a1)


“The Trolley Problem” is the name Judith Jarvis Thomson has given to a difficult problem in moral philosophy and legal theory. The problem arises by considering a series of cases, all of which involve a choice of evils. Many, but not all of these cases, involve an out-of-control trolley about to run over a group of five people. In each case we are asked for our intuitive judgment as to whether it would be permissible to save the five people at risk when doing so would require the death of, or the imposition of a high risk of death on, another human being.



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1. Thomson, Judith Jarvis, Killing, letting Die, and the Trolley Problem and The Trolley problem, in Rights, Restitution and Risk (Parent, William ed., 1986); see also ch. 7, The Trolley problem, in The Realm of Rights (1990). Thomson credits Philipps Foot with first devising the problem in Foot's essay, The Problem of Abortion and the Doctrine of the Double Effect. The essay is reprinted in Foot's collection of essays, Virtues and Vices (1978).

2. Id.

3. Raz, Joseph, The Morality of Freedom 357–66 (1986).

4. Thomson, , The Trolley Problem, supra note 1, at 96.

5. For the purpose of understanding the principle at stake in the Trolley Problem cases, we must limit our knowledge of the people at risk in these cases to just what Thomson and Foot tell us about them. We must not make the cases more complicated by supposing that the one person on the right spur of track, for example, is our spouse or child or some other person special to us.

6. Foot, , supra note 1, at 23.

7. Id.

8. Thomson, , The Trolley Problem, supra note 1, at 94.

9. Foot, Philippa, Killing and Letting Die, in Abortion: Moral and Legal Perspectives (Garfield, Jay L. & Hennessey, Patricia eds., 1984). She describes Rescue 1 at 179.

10. Id. at 179.

11. Thomson, , Killing, Letting Die, and the Trolley Problem, supra note 1, at 8486, 8992.

12. Foot, , The Problem of Abortion and the Doctrine of the Double Effect, supra note 1, at 24.

13. Thomson, , The Trolley Problem, supra note 1, at 98.

14. Id. at 95.

15. Foot, , supra note 1, at 24.

16. Thomson, , The Trolley Problem, supra note 1, at 95.

17. John Harris, however, might think it is permissible if the healthy young man had been fairly selected in a “survival lottery.” See The Survival Lottery, 50 Philosophy, 81 (1975).

18. Foot, , supra note 1, at 27.

19. This argument is implicit in Foot, , supra note 1, at 27.

20. Id. at 27–28.

21. Thomson, , The Trolley Problem, supra note 1, at 96.

22. Id.

23. Id. at 97.

24. Foot does not think so, however. She believes bystander at the switch is a “special” case “in that we have here the diverting of a fatal sequence and not the starting of a new one.” See, Foot, , supra note 9, at 183. She does not explain, however, what makes killing someone by diverting a preexisting threat a special case of killing. In Section III of this paper I argue that the distinction between diverting a preexisting threat and originating a new one is not the distinction underlying our intuitive judgments in the Trolley Problem cases.

25. This case is similar to a case that Thomson presents in The Trolley Problem, supra note 1, at 109. Thomson calls her version of the case fat man. In her version of the case the agent is a bystander standing next to an enormously fat man on an overpass.

26. Similarly, everyone with whom Thomson has discussed her version of the case says this would not be permissible. The Trolley Problem, supra note 1, at 109.

27. Foot, , The Problem of Abortion, supra note 1, at 28, and Killing and Letting Die, supra note 9, at 183–84. In the latter essay. Foot attempts to distinguish transplant (Surgeon Lets Die) from rescue (Choice of Tracks) on the basis that in the former case, but not in the latter, “the ‘direct’, i.e., deliberate intention of evil is what makes it morally objectionable to allow the (man) to die.” I find this answer unsatisfactory in part because Foot's criticism of the Doctrine of the Double Effect makes doubtful the thesis that a significant moral difference exists between the “direct” intention of the surgeon in transplant (Surgeon Lets Die) and the “oblique” intention of the trolley driver in rescue (Choice of Tracks).

28. This is the solution Thomson proposes in The Trolley Problem, supra note 1, at 103–12. She abandons this proposal in The Realm of Rights at 179, note 2. On the other hand, the solution Thomson proposes in ch. 7 of The Realm of Rights has been effectively criticized by Gert, Bernard in Transplants and Trolleys, 53 Phil. & Phenomenological Res. 173–79 (1993).

29. Immanuel Kant argued that in order for an act to be moral, it had to be consistent with the fundamental principle of morality, which Kant called the Categorical Imperative. He formulated it in several different ways. The formula Thomson has in mind is the formula of “The End in Itself,” which is “Act in such a way that you always treat humanity, whether in your own person or in the person of any other, never simply as a means, but always at the same time as an end.” See Kant, Immanuel, Groundwork of the Metaphysics of Morals 96 (Paton, H.J. trans., 1964).

30. Thomson's interpretation of the Categorical Imperative is, arguably, not technically correct. See infra 31. But her interpretation of the Imperative has the merit of making the Imperative appear to be an initially plausible solution to the Trolley Problem.

31. See The Trolley Problem, supra note 1, at 100–1. As Thomson uses the expression “a means to an end” in its ordinary sense she ends up interpreting Kant's Imperative in a manner that makes it sound like the Doctrine of the Double Effect. This interpretation of the Categorical Imperative is probably not the interpretation Kant would offer.

While Kant accepts the Necessity defense as an excuse in The Metaphysics of Morals (in the “Appendix to the Introduction to the Doctrine of Right”) in cases which are not Trolley Problem cases, Kant's appears to reject the lesser-evil defense as a justification, in cases which are similar to Trolley Problem cases. See On a Supposed Right to Lie From Altruistic Motives, in Kant, Immanuel, Critique of Practical Reason and Other Writings in Moral Philosophy 346–50 (Beck, L.W. ed. and trans., 1949).

Kant's Categorical Imperative can be plausibly interpreted, therefore, as prohibiting killing the one in all the Trolley Problem cases and not just in fat man on the overpass, transplant (Surgeon Kills) and transplant (Surgeon Lets Die).

Of course, if this is the correct way to interpret the Categorical Imperative, then it cannot account for our bewildering judgments in the Trolley Problem cases.

32. This case is very similar to Thomson's case of loop variant of bystander at the switch. See Thomson, , The Trolley Problem, supra note 1, at 101.

33. Thomson, , The Trolley Problem, supra note 1, at 102.

34. Id. at 101–2.

35. Foot, , supra note 9, at 179. She did not devise this case, however, for the purpose of showing the inadequacy of the Categorical Imperative as a solution to the Trolley Problem. Rather, she uses it to demonstrate her thesis that there is a morally significant difference between killing and letting die.

36. She calls this case rescue it. Her rescue i case is the case I discussed under the name rescue (Choice of Tracks).

37. Foot, , supra note 9, at 179–80.

38. Stephen, James F., A history of the criminal Law of England 110 (London, Macmillan 1883).

39. Section 3.02 of the Model Penal Code formulates the lesser-evil defense as follows: “(1) Conduct that the actor believes to be necessary to avoid a harm or evil to himself or to another is justifiable, provided that: (a) the harm or evil sought to be avoided by such conduct is greater than that sought to be prevented by the law defining the offense charged; and (b) neither the code nor other law defining the offense provides exceptions or defenses dealing with the specific situation involved; and (c) a legislative purpose to exclude the justification claimed does not otherwise plainly appear. (2) When the actor was reckless or negligent in bringing about the situation requiring a choice of harms or evils or in appraising the necessity for his conduct, the justification afforded by this Section is unavailable in a prosecution for any offense for which recklessness or negligence, as the case may be, suffices to establish culpability.”

To this formulation should be added the additional requirement that the means used to bring about the lesser evil must be the least destructive means available to the agent. See Fletcher, George, Rethinking Criminal Law 774–75 (1978).

40. Stephen seems to have thought that the necessity defense that applied to the unfortunate ship pilot is an excuse; see supra note 38, at 105. If, however, it is permissible for the ship's pilot to ram the smaller vessel, then the defense is a justification. See Austin, J.L., A Plea for Excuses, 57 Proc. Aristotelian Socy 130 (1957).

41. The difficulty people have had in understanding when the defense should be available to criminal-law defendants and when it should not be, plus the fact that it is generally unjustifiable and inexcusable to kill innocent human beings, is surely sufficient to explain why relatively few states have statutorily codified the defense.

Only twenty of the American states have ever statutorily enacted some form of the defense: Alabama (Ala. Code § 1 3A–3–29 [1982] [repealed] [necessity]); Alaska (Alaska Stat. § 11.881.320 [Cum. Supp. 1982]); Arkansas (Ark. Stat. Ann. § 41–504 [1977] [justification; choice of evils]; Colorado (Cob. Rev. Stat. § 18–1–702 [1978] [choice of evils]; Delaware (Del.Code Ann. tit. 11, § 463 [1979] [choice of evils]); Georgia (Ga.Code Ann. § 1 6–3–20 [6] [Michie 1982] [justifications that stand on same footing of reason and justice as those enumerated, are recognized]); Hawaii (Hawaii Rev.Stat. § 703–302 [1976] [choice of evils]); Illinois (Ill.Ann. Stat. ch.38, § 7–13 [Smith-Hurd 1972] [necessity]); Indiana (Ind.Code Ann. §35–46–3–2, which codifies a defense to the charge of cruelty to animals that is available to one who either kills a seriously injured animal to prevent its prolonged suffering or kills an animal to prevent injury to himself, injury to another person, or substantial damage to or destruction of property); Kentucky (Ky.Rev.Stat. § 503.030 [1975] [choice of evils)); Maine (Me.Rev.Stat. Ann. tit. 17-A, §103 [1983] [competing harms]); Missouri (Mo. Ann.Stat. § 563.026 [Vernon 1979] (justification, generally]); Nebraska (Neb.Rev.Stat. § 28–1407 [1979] [choice of evils]); New Hampshire (N.H.Rev.Stat.Ann. § 627:3 [1974] [competingharms]; New Jersey (NJ.Stat.Ann. § 2C:3–2 [West 1982] [necessity and other justifications in general]; New York (N.Y. Penal Law § 35.05 [McKinney 1975] [justification, generally]); Oregon (Or.Rev.Stat. § 161.200 [1981] [choice of evils]); Pennsylvania (18 Pa.Cons.Stat.Ann. §503 [Puntan 1983] [justification, generally]); Texas (Tex.Penal Code Ann. tit.2, § 9.22 [Vernon 1974] [necessity]); Wisconsin (Wis.Stat.Ann. § 939.47 [West 1982] [necessity]).

Of these twenty suites, one has already repealed its statute (Alabama), The statute of another state (Indiana) applies only to a charge of cruelty to animals. Two states (Kentucky and Missouri) do not permit their choice-of-evils defense to apply to a charge of intentional homicide. Wisconsin's statute applies only to reduce a charge of first degree intentional homicide to second degree intentional homicide.

42. Prosser, William. Handbook of the Law of Torts 124–27 (4th ed. 1971).

43. This could happen, for example, to either the trolley driver in Trolley Driver and Fat Man on the Bell. Curve Loop or to the bystander in Bystander at the Switch. See Vincent v. Lake Erie Transportation Co., 109 Minn. 456, 124 N.W. 221 (1910) for the proposition that we are legally obligated to compensate those innocent people whose claims we justifiably infringe. The trolley driver's and the bystander's remedy in tort would be to obtain indemnification from the trolley company. See Prosser, , supra note 43, at 311–13.

44. Thomson, , The Trolley Problem, supra note 1, at 107.

45. Foot, , supra note 1, at 29.

46. id.

47. Thomson, , The Trolley Problem, supra note 1, at 107–8; Foot, , supra note 9, at 183.

48. In fairness to Thomson, there is reason to believe she does not now accept Foot's argument that the hospital staffs liability in tort to the estate of the deceased patient in Hospital shows that it would be morally impermissible for them to gas the patient. In the Realm of Rights at 93–96, Thomson discusses the moral obligation to compensate those innocent people whose claims we justifiably infringe.

Other students of the Trolley Problem, however, continue to make the mistake of inferring moral impermissibility of an act from the existence of tort liability for the act. Clark, Michael, for example, makes this mistake in his essay Sacrificing One to Save Many, 12 J. Applied Phil. 192 (1995).

49. Thomson, Judith, Self-Defense, 20 Phil. & Pub. Aff. 283310 (Fall 1991) defends this thesis.

50. Thomson comes to the same conclusion but for different reasons in The Realm of Rights, supra note 1, at 179.

51. Raz, , supra note 3, at 359–60, 365.

52. Id. at 359.

53. Id. at 360.

54. Id. at 362, 364. At 322 Raz offers the following simple definition of incommensurability: A and B are incommensurate if it is neither true that one is better than the other nor true that they are of equal value.

55. Id. at 362.

56. See White, Alan, The Grounds of Liability 60 (1985). The argument just sketched is intended to be a response to Norcross, Alastair, who, in Comparing Harms: Headaches and Human Lives, 26 Phil. & Pub. Aff. 133167 (Spring 1997), argues at 137 there is no rational choice a moral agent can make when faced with incommensurate evils. I do not propose, however, to extend this analysis from Trolley Problem cases (in which human lives are at stake) to the problem that Norcross addresses, which is one in which a human life is being weighed against a vast number of people having a fairly minor headache.

57. Raz, , supra note 3, at 325, 326.

58. See Feinberg, Joel. Harm to Others 188–93 (1984). Another important criterion may be the pain the harm causes. Feinberg believes another important criterion is whether, in harming the victim, the agent uses the victim as a mere means to an end. Later in this section I argue that this is not an important criterion for evaluating harms, at least in a choice-of-evils situation.

59. More precisely, the harms are incommensurate if one option will result in certain death for the smaller group of people while it is not certain that the other option will eventuate in the deaths of the larger group of people.

60. Raz, , supra note 3, at 360. The passage I have in mind reads as follows:

It is impossible to warn often enough that from the impossibility of comparing the degree of badness of two options it does not follow that they are bad to the same degree. Such equality of evils is not a real possibility where the options differ from each other in a significant way. It is to be found only when one chooses not only between evils but between two forms of exactly the same evil. This happens when one's only choice is between the use of two similar poisons, etc.

I interpret Raz to be saying here that what makes the two evils commensurate is the fact that they are two similar poisons. What makes them not only commensurate but equal is the fact that the same number of people (presumably), if not the very same people, will be affected by the consumption of either poison.

61. Even if they were chained to a rock in a manner similar to that in which the man is chained to the track, there would still be at least one significant moral objection to running over the man on the track: It would be an exercise in futility. How would the trolley driver propose to extricate the five from their chains if he cannot extricate the man chained to the track?

62. This approach is suggested by the trial court's reasoning in United States v. Holmes, 26 Federal Cases 360 (1842), an overcrowded lifeboat case.

63. Thomson, in her discussion of transplant (Surgeon Kills) in the realm of Rights, “bypasses” the idea that one of the patients could be cut up to supply parts for the others; at 135.

64. Feinberg, , supra note 58, at 189 asserts that when we evaluate the magnitude of a harm done to a victim we ought to consider whether, in harming the victim, we are using him as a mere means. Feinberg is not discussing there, however, harms done to victims in a choice-of-evils situation.

65. Our somewhat uneasy intuitive moral judgment that it is morally permissible to deflect the trolley toward the fat man in Fat Man on the Bell Curve Loop supports this conclusion that the insult done to the fat man by treating him as a mere means to an end plays only a minor role in our comparing the risk of the harm which deflecting the trolley will impose on him with the harm currently threatening the five workers on the track straight ahead.

66. The sinking of the U.S.S. Squals, an American Navy submarine, off the coast of Portsmouth, New Hampshire, on May 23,1939, presented its commanding officer with such a choice. The cover of the main induction valve failed to close properly during a test dive in water with a depth of 230 feet. This resulted in the flooding of half the submarine's compartments. The commanding officer, Lieutenant O. F. Naquin, ordered the interior hatches of the submarine closed in order to prevent the entire submarine from flooding. He lost half his crew in the flooded compartments.

The Court of Inquiry found that Lt. Naquin displayed outstanding leadership during the sinking of the Squalus and the rescue of her survivors and recommended that no further proceeding be taken against him.

Although Lt. Naquin clearly hastened the death of the sailors in the flooding compartments by preventing their escape, he was clearly presented with a choice of two commensurate evils: hastening the death of half his crew in the flooding compartments or subjecting his entire crew to death by drowning. It is not clear to me that the fact that he faced a choice of commensurate evils is more important in evaluating his conduct than is the fact that he was powerless to save the members of his crew who were in the flooding compartments in any event.

Nat A. Burrow's Blow All Ballast!: The Story of the Squalus (1940) is a highly readable journalistic account of the sinking of the Squalus and the remarkable rescue of her survivors. The transcript of the inquest into the sinking of the Squalus is in the Suitland Reference Branch of the National Archives in Washington, D.C.

67. Raz, , supra note 3, at 358.

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