Runaway Trolley, Never Coming Back

The trolley problem is a relatively standard problem in ethics that arose from Phillipa Foot in 1967:

Suppose…the driver of a runaway tram which he can only steer from one narrow track on to another; five men are working on one track and one man on the other; anyone on the track he enters is bound to be killed.

The question posed is what should the driver of the runaway trolley do. The problem is complicated by the ethical and moral frameworks that surround causation. From a strictly utilitarian point of view, the analysis is straightforward: The driver should steer the trolley onto the track with one person. The single person will die, but five will be saved. This is outlined in Star Trek II: The Wrath of Khan when Spock summarizes the utilitarian stance by saying, “Logic clearly dictates that the needs of the many outweigh the needs of the few.”

But ethics and morality come into play by asking the train driver to make a decision. If the train will kill five if no action is taken, some interpret this as acceptable. While it may be, by some objective standard, better to only kill one, that requires the positive action of the driver to be the cause, a situation some find untenable. However, studies have shown that something around 9 in 10 people will make the choice to sacrifice one to save five.

There are a number of interesting variants. One of them further explores the relationship between cause and effect and the relationship to ethics. Judith Jarvis Thomson posed this question,

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 putting something very heavy 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?

In this example, many object to the situation before realizing the test is about ethics and not mechanics. And, the logic of utilitarianism still holds. It is better that five should live at the expense of one. But ethically and morally, the analysis breaks down differently because the proposed victim, the very fat man, was not really a party to the problem to begin with. Therefore, it is unreasonable to draw him into the problem now, especially as the agent of his own demise. And many agree with this reasoning, as studies have shown respondents are less likely to push the man.

These dilemmas, which are dilemmas, unlike the Monty Hall problem, present a different aspect of the challenge of risk assessment, and estimating cost. In each case, due to the problem set up, death is certain, so making a decision should be straightforward. However, the original trolley problem and Thomson’s variant, plus many others, show the distinction between the straightforward utilitarian analysis and the results of ethical and moral thinking. Questions about this type of ethical dilemma date back to at least the 13th Century when Thomas Aquinas proposed the doctrine of double effect. In his analysis, it acceptable to cause harm for the benefit of others, provided the harm is not the intended effect.

In addition, these are not mere abstract problems. The ideas underlying this turn up in governmental decision processes, known as public choice theory. One important decision rule focuses on Pareto efficiency. A solution is considered Pareto efficient if someone is made better off without making anyone worse off. That is a surprisingly difficult bar to clear and a lesser standard is the Kaldor-Hicks criterion, wherein those who are made better off compensate those who are made worse off.

Looking forward, these questions are coming up in the context of driverless cars. A car driving must make decisions about changing lanes and turning and when to do that. While driverless cars are have an incredible safety record, it may come to pass that a driverless car is forced into no-win situation and risk its own occupants or the occupants of another car.1

It is important to recognize there is no correct answer to the trolley problem. It is a thought experiment designed to elicit critical thinking. If you encounter it in the real world, the correct result is whatever you can live with. However, seeing it come up in other contexts show where subtle variants can create interesting solutions that are distinct from each other.

Image by Mike Knell / Wikimedia Commons.

  1. Also, yes, Star Trek II again.