Trolley problem

The trolley problem is a thought experiment in ethics, first introduced by Philippa Foot [Philippa Foot, "The Problem of Abortion and the Doctrine of the Double Effect" in "Virtues and Vices" (Oxford: Basil Blackwell, 1978)] , but also extensively analysed by Judith Jarvis Thomson [Judith Jarvis Thomson, "Killing, Letting Die, and the Trolley Problem", 59 The Monist 204-17 (1976)] [Judith Jarvis Thomson, "The Trolley Problem", 94 Yale Law Journal 1395-1415 (1985)] and, more recently, by Peter Unger [Peter Unger, "Living High and Letting Die" (Oxford: Oxford University Press, 1996)] and Frances Kamm [Francis Myrna Kamm, "Harming Some to Save Others", 57 Philosophical Studies 227-60 (1989)] . Similar problems have traditionally been addressed by criminal lawyers and are sometimes regulated in penal codes, especially in civil legal systems. A classical example of these problems became known as "the plank of Carneades", designed by Carneades to attack Stoic moral theories as inconsistent. Outside of the domain of traditional philosophical discussion, the trolley problem has been a significant feature in the field of neuroethics, which tends to approach philosophical questions from a neuroscientific approach.


The problem is this [Philippa Foot, "The Problem of Abortion and the Doctrine of the Double Effect" in "Virtues and Vices" (Oxford: Basil Blackwell, 1978)] :

: A trolley is running out of control down a track. In its path are 5 people who have been tied to the track by a mad philosopher. Fortunately, you can flip a switch which will lead the trolley down a different track to safety. Unfortunately, there is a single person tied to that track. Should you flip the switch?

A utilitarian view asserts that it is permissible to flip the switch. According to simple Utilitarianism, flipping the switch would be not only permissible, but, morally speaking, the better option (the other option being no action at all).

While simple utilitarian calculus seeks to justify this course of action, some non-utilitarians may also accept the view. Opponents might assert that, since moral wrongs are already in place in the situation, flipping the switch constitutes a participation in the moral wrong, making one partially responsible for the death (when otherwise the mad philosopher would be the sole culprit). Additionally, opponents may point to the incommensurability of human lives.

It might also be justifiable to consider that simply being present in this situation and being able to influence its outcome constitutes an obligation to participate. If this were the case, then deciding to do nothing would be considered an immoral act.

Related problems

The initial trolley problem becomes more interesting when it is compared to other moral dilemmas.

The fat man

One such is that offered by Judith Jarvis Thomson:

: As before, a trolley is hurtling down a track towards five people. You are on a bridge under which it will pass, and you can stop it by dropping a heavy weight in front of it. As it happens, there is a very fat man next to you - your only way to stop the trolley is to push him over the bridge and onto the track, killing him to save five. Should you proceed?

Resistance to this course of action seems strong; most people who approved of sacrificing one to save five in the first case do "not" approve in the second sort of case. This has led to attempts to find a non-relevant moral distinction between the two cases.

One clear distinction is that in the first case, one does not intend harm towards anyone - harming the one is just a side-effect of switching the trolley away from the five. However, in the second case, harming the one is an integral part of the plan to save the five. This is an argument Shelly Kagan considers, and ultimately rejects, in "The Limits of Morality". [Shelly Kagan, "The Limits of Morality" (Oxford: Oxford University Press, 1989)]

So, some claim that the difference between the two cases is that in the second, you intend someone's death to save the five, and this is wrong, whereas in the first, you have no such intention. This solution is essentially an application of the doctrine of double effect, which says that you may take action which has bad side-effects, but deliberately intending harm (even for good causes) is wrong.

On the other hand, Thomson argues that an essential difference between the original trolley problem and this version with the fat man, is that in the first case, you merely deflect the harm, whereas in the second case, you have to do something to the fat man to save the five. Thomson says that in the first case, nobody has any more right than anyone else not to be run over, but in the second case, the fat man has a right not to be pushed in front of the trolley.

Act utilitarians deny this. So do some non-utilitarians such as Peter Unger, who rejects that it can make a substantive moral difference whether you bring the harm to the one or whether you move the one into the path of the harm. Note, however, that rule utilitarians do not have to accept this, and can say that pushing the fat man over the bridge violates a rule that adherence to is necessary for bringing about the greatest happiness for the greatest number.

The track that loops back

The claim that it is wrong to "use" the death of one to save five runs into a problem with "loop" variants like this:

:As before, a trolley is hurtling down a track towards five people. As in the first case, you can divert it onto a separate track. On this track is a single person. However, beyond that person, this track loops back onto the main line towards the five, and if it weren't for the presence of that person, who will stop the trolley, flipping the switch would not save the five. Should you flip the switch?

The only difference between this case and the original trolley problem is that an extra piece of track has been added, which seems a trivial difference (especially since the trolley won't travel down it anyway). So intuition may suggest that the answer should be the same as the original trolley problem – one may flip the switch. However, in this case, the death of the one actually is part of the plan to save the five.

The loop variant may not be fatal to the "using a person as a means" argument. This has been suggested by M. Costa in his 1987 article "Another Trip on the Trolley", where he points out that if we fail to act in this scenario we will effectively be allowing the five to become a means to save the one. If we do nothing then the impact of the trolley into the five will slow it down and prevent it from circling around and killing the one. As in either case some will become a means to saving others, then we are permitted to count the numbers. This approach requires that we downplay the moral difference between doing and allowing.


Here is an alternate case, due to Thompson, containing similar numbers and results, but without a trolley:

: A brilliant transplant surgeon has five patients, each in need of a different organ, each of whom will die without that organ. Unfortunately, there are no organs available to perform any of these five transplant operations. A healthy young traveler, just passing through the city the doctor works in, comes in for a routine checkup. In the course of doing the checkup, the doctor discovers that his organs are compatible with all five of his dying patients. Suppose further that if the young man were to disappear, no one would suspect the doctor.

As rare as it is to find someone who does not think we should turn the trolley, it is even rarer to find someone who thinks it is permissible for the doctor to murder this patient and harvest his organs. (A rare few utilitarians, such as Alastair Norcross, think that this "might" be acceptable under certain exceedingly unlikely circumstances.)Clarifyme|date=March 2008 Yet both cases seem to involve a choice between one life and five.

The man in the yard

Unger argues extensively against traditional non-utilitarian responses to trolley problems. This is one of his examples:

: As before, a trolley is hurtling down a track towards five people. You can divert its path by colliding another trolley into it, but if you do, both will be derailed and go down a hill, and into a yard where a man is sleeping in a hammock. He would be killed. Should you proceed?

Responses to this are partly dependent on whether the reader has already encountered the standard trolley problem (since there is a desire to keep one's responses consistent), but Unger notes that people who have not encountered such problems before are quite likely to say that, in this case, the proposed action would be wrong.

Unger therefore argues that different responses to these sorts of problems are based more on psychology than ethics – in this new case, he says, the only important difference is that the man in the yard does not seem particularly "involved". Unger claims that people therefore believe the man is not "fair game", but says that this involvedness cannot make a moral difference.

Unger also considers cases which are more complex than the original trolley problem, involving more than just two results. In one such case, it is possible to do nothing and let five die, or to do something which will (a) save the five and kill four (passengers of one or more trolleys and/or the hammock-sleeper), (b) save the five and kill three, (c) save the five and kill two, or (d) save the five and kill one. Most naïve subjects presented with this sort of case, claims Unger, will choose (d), to save the five by killing one, even if this course of action involves doing something very similar to killing the fat man, as in Thomson's case above.

In neuroethics

In taking a neuroscientific approach to the trolley problem, Joshua Greene [ [ Homepage of Joshua Greene] ] under Jonathan Cohen decided to examine the nature of brain response to moral and ethical conundra through the use of fMRI. In their more well-known experiments [Joshua D. Greene, "The secret joke of Kant’s soul", in Moral Psychology, Vol. 3: The Neuroscience of Morality, W. Sinnott-Armstrong, Ed., (Cambridge, MA: MIT Press)] , Greene and Cohen analyzed subjects' responses to the morality of responses in both the trolley problem involving a switch, and a footbridge scenario analogous to the fat man variation of the trolley problem. Their hypothesis suggested that encountering such conflicts evokes both a strong emotional response as well as a reasoned cognitive response that tend to oppose one another. From the fMRI results, they have found that situations highly evoking a more prominent emotional response such as the fat man variant would result in significantly higher brain activity in brain regions associated with response conflict. Meanwhile, more conflict-neutral scenarios, such as the relatively disaffected switch variant, would produce more activity in brain regions associated with higher cognitive functions. The potential ethical ideas being broached, then, revolve around the human capacity for rational justification of moral decision making.

ee also

* Consequentialism
* Deontology
* Principle of double effect
* Violinist (thought experiment)
* Virtue ethics
* Debate over the atomic bombings of Hiroshima and Nagasaki


External links

* [ Runaway Trolley and other Moral Dilemmas]

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