What would they do?
Each card applies one ethical theory, mechanically, to the tracks above. The theories are simplified so they can be computed, but each captures the core of a real position. Change a number and watch the verdicts move.
Real-world examples
Real decisions rarely come with clean numbers. Each example is tagged by how much to trust its figures: historical recorded counts, approximate rounded from sources, illustrative invented to show the shape of the choice, contested disputed by historians, and thought experiment / fiction. Load one, decide, and only then read what actually happened.
Your moral profile
Every time you run the trolley on a loaded example, your lever choice is compared with each theory’s verdict. Over many examples a pattern appears. (Stored only in this browser.)
Background
Where it comes from
Philippa Foot posed the runaway tram in 1967, in a paper on abortion and the doctrine of double effect. She paired it with a judge who could stop a riot by framing an innocent man: also five lives for one, yet almost everyone answers the two cases differently. Judith Jarvis Thomson named it “the trolley problem” in 1976 and added the footbridge, the loop and the transplant surgeon. The real puzzle is not “five or one?” but why the answer changes when the arithmetic does not.
Earlier versions exist. Frank Chapman Sharp put one in a 1905 questionnaire for Wisconsin undergraduates, with the switchman’s own child on the side track. German legal scholars Karl Engisch (1930) and Hans Welzel (1951) discussed similar cases.
The theories in the cards
Utilitarianism minimises expected deaths. Life-years (the logic behind QALYs and some pandemic triage) minimises years of life lost. Strict deontology forbids killing the innocent who have not consented, whatever the numbers. The doctrine of double effect allows foreseen but unintended harm if it is proportionate, but not harm used as a means. Threshold deontology weighs harm you cause more heavily than harm you allow. Partiality lets special relationships count. John Taurek’s 1977 “Should the Numbers Count?” argues they shouldn’t: give everyone an equal chance and flip a coin.
What psychology found
Around 90% of survey respondents divert in the switch case, but most refuse to push in the footbridge case. Joshua Greene’s fMRI work (2001) linked “personal” dilemmas to emotional brain regions. MIT’s Moral Machine (2018) gathered about 40 million decisions from 233 countries and territories and found broad agreement on sparing more lives and younger lives, with clear cultural differences in how strongly.
Why critics say it misleads
Real dilemmas come with uncertainty, time pressure, unclear defaults, and people who can run away. Hence the lever-reliability slider and the risk percentages. Germany’s 2017 ethics commission on automated driving said genuine dilemmas “cannot be standardized” and that cars must be designed to avoid accidents in the first place. Masahiro Morioka notes that the dead never get a say in trolley framings. In law, deliberate killing is rarely excused by necessity (R v Dudley and Stephens), while cost-benefit reasoning is everywhere in negligence (Learned Hand’s B < PL).