Option 1: Do nothing and let five die.
Option 2: Flick a switch that redirects the trolley onto a side-track with four innocent people who cannot escape on it, killing them and saving the five
Option 3: Flick a switch that redirects the trolley onto a raised side-track with three innocent large men who cannot escape on it, killing them and saving the five.
Option 4: Push an innocent very large man, who is holding another innocent large man and standing on a footbridge, into the path of the trolley, killing them and saving the five.
Option 5: Push an innocent very large man on a foot bridge into the path of the trolley, killing him and saving the five.The pedestrian takes Option 5, and as a result the innocent very large man dies and the five innocent people are saved.
Select which answer best fits your opinion (chose one and only one response):
A: Given the situation, the pedestrian’s action was morally permissible
B: Given the situation, the pedestrian’s action was not morally permissible
According to many philosophers, including Philippa Foot (1967) and Judith Jarvis Thomson (1976), the vast majority of people realize that pushing the very large man in this kind of situation is not morally permissible (i.e. morally speaking, it’s not OK to push the guy). Empirical research on trolley scenarios like this are largely in agreement; the proportion of respondents reporting that pushing the very large man (killing one to save five) is morally permissible ranges from about 11% (Hauser et al. 2007) to 18% (Kelman and Kreps 2014). BUT, these empirical studies, and the views of Foot and Thomson, are based on versions of the scenario that at least imply that only two options are available to the agent: to push or not to push. For an example of a two-option version, consider the above five-option scenario with options 2, 3, and 4 omitted.
Among the uses of experimental philosophy (doing experiments to help resolve philosophical problems), are:
1) Testing the claims philosophers make about the proportion of people who have this or that intuition, or believe this or that proposition, etc. And,I conducted a paper-based survey of 468 undergraduate students so as to run these kinds of tests in relation to the ‘pushing the very large man’ (AKA ‘foot bridge’) trolley scenario. More specifically, I wanted to find out whether including several, instead of two, options had an effect on how people reported the moral status of pushing the very large man in a ‘foot bridge’ trolley scenario. The basic method for conducting such an investigation is to randomly assign each individual in the sample either the two-option version of the scenario or a several-option version of the same scenario. In my study, I randomly assigned one of the following three versions: the two-option version, the three-option version, or the five-option version.
2) Comparing intuitions about similar scenarios to test whether certain manipulations tend to produce different results (e.g., to test whether a thought experiment inadvertently elicits a bias by the inclusion of some purportedly irrelevant fact)
The five-option scenario above is the same as I used in my study. The three-option version followed the same pattern, but omitted options 2 and 4 from the five-option version. Similarly, the two-option version omitted options 2, 3, and 4.
As you can see in the chart below, the more options in the scenario, the greater the proportion of respondents indicating that pushing the very large man is morally permissible. The differences between the two-option version and the other versions are both statistically significant (p<0.05). The difference between the three- and five-option versions was not statistically significant (p=0.1213). These results mean that we can be 95% or more confident that the differences between two-option version and the other versions are not the product of chance. Notice also, that the majority verdict changes position as we move from the two- to the five-option version. In the two-option version, the majority views pushing the very large man as morally impermissible, but in the five-option case an even greater majority views pushing the very large man as morally permissible. This is interesting result #1.
Why might including several-options in the scenario change the reported judgments in this way? Peter Unger (1996) has argued for ‘Liberationism’, i.e., that including intervening options in established two-option thought experiments can liberate readers’ judgments by inducing them to think more deeply about which option reduces the most harm to innocent people. According to Liberationism, then, reasonable respondents should report more utilitarian judgments about the morality of particular actions in several-option setups compared to two-option setups.
What do you think could have caused this result? Also, assuming the cause of the difference is not pernicious, think about the implications of this finding for the trolley problem and, potentially, all those other famous two-option scenarios!
Interesting result #2 is that 41.8% of respondents to the two-option scenario reported pushing the very large man as morally permissible. This is more than double the proportion found in other published studies of ‘foot bridge’ trolley scenarios, and far more than anecdotal evidence from the ‘coal face’ of undergraduate (raise-your-hand-if-you…) lecturing would suggest. Was my result anomalous? My collaborators conducted some online surveys using very similar scenarios with very similar results. When I observed Genevieve Wallace polling students on this scenario using clickers, the results were also similar to my results here. So, it seems this is a genuine mystery. Why are all the results I have first-hand experience of different to all of the results that I don’t have that experience of?
Please help me solve these mysteries!
Department of Philosophy
Many thanks to Peter Unger and Justin Sytsma for advice and comments on the study set up, analysis, and discussion. Thanks also to the Provost’s Research Incentive Fund for effectively bankrolling the study.
Foot, P. (I967). The Problem of Abortion and the Doctrine of the Double Effect, The Oxford Review, 5: 5-15.
Hauser, M., Cushman, F., Young, L., Kang‐Xing Jin, R., & Mikhail, J. (2007). A Dissociation Between Moral Judgments and Justifications. Mind & language, 22(1): 1-21.
Kelman, M., & Kreps, T. A. (2014). Playing with Trolleys: Intuitions About the Permissibility of Aggregation. Journal of Empirical Legal Studies, 11(2): 197-226.
Thomson, J. J. (1976). Killing, Letting Die, and the Trolley Problem. The Monist, 59: 204-217.
Thomson, J. J. (1985). The Trolley Problem. Yale Law Journal, 94: 1395-1415.
Unger, P. (1996). Living High and Letting Die: Our Illusion of Innocence. Oxford University Press: New York.