The evil trolley problem

On Tuesday I posted a question on Twitter (prompted by a remark by @bowmanthebard). The question involved a version of the trolley problem, in which one has to choose between letting die and actively killing, but with the twist that the motive for choosing the active option is not to minimize loss of life (in this version it might actually increase it) but to preserve a life especially dear to one.

As the question generated some interest, I thought I would set out the thought experiment in more detail here. Another Twitter user @gjfitzgerald described my question as evil, since there is no way to answer it without guilt, so I call it The Evil Trolley Problem (not a perfect name, I admit, since it’s ambiguous). I’m not an ethicist, and I don’t know if this particular scenario has been previously discussed in the literature (if it has, I’d be grateful for references), though I’m sure the underlying issues have.

Here is the problem:

You are walking by the railway line, where a group of local children are playing. Suddenly, there is a shout and you see that a runway trolley is thundering down the track. You run to warn the children and see that one child is trapped on the line. With horror you realize that it is your own child. The trolley will certainly kill your child if you do not act. Luckily, you are close to the points, and by operating a manual lever you can divert the trolley onto another track. But as you grasp the lever, you notice that another child, not known to you, is trapped on the other track. If you pull the lever, the trolley will certainly kill them.

What would you do? There are only seconds left and there is no other option. Would you sacrifice an unknown child to save your own? If you would switch the trolley, would do the same if it it would result in more deaths? What if there were two children trapped on the other line or if there were a school bus stalled there? How many children would you sacrifice to save your own child?

The scenario is of interest because what most of us would do in the imagined situation is in contrast to what moral theory tells us we should do. I suspect that most of us would switch the trolley, even if it would result in many deaths. Yet I doubt if there are many moral theories that would dictate that course, or even judge it permissible, and most legal systems would, I assume, class it as murder. This in turn raises wider questions about how far moral theory should bend to human nature, and how we can reconcile our intense preference for our kin with our ideals of altruism and egalitarianism.

Posted in Tricks of the mind and tagged , .


  1. Evolutionary psychology and game theory offer interesting analysis and pretty accurate predictive capability in these types of cases. There’s a lot of potential influencing factors, including how “random” these other children are, how your social reputation might be affected, and what the law (convention) says you should do. From a pure DNA standpoint, and what evolutionary theory would predict, I agree with Keith Frankish that our instincts in the heat of the moment will push us to allow many children to die to save one’s own. This is an example of how we might push social conventions to encourage more cooperation in an attempt to counterbalance the part of our brain with instincts that lead to a more “selfish” outcome. (However, from my limited neuroscience understanding, in the heat of the moment it is less likely these social influences and less immediate consequences will have a major influence– timing is an important factor).

    This Hamiltonian problem is intriguing because evolutionary theory would predict one to save the 5 nieces and nephews (5*.25 = 1.25 vs. 2*.5 = 1), but my intuition seems slightly in favor of the siblings---it's a close call though, and probably depends on everyone's age and how I'm feeling that day about my older bullying brother!

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