The trolley problem asks whether you may harm one person to save several. The philosopher who gave the puzzle its name spent decades on it, and then reversed her own answer.
A runaway trolley is heading for five people. You can pull a switch and send it down a side track, where it will kill one person instead. Most people say you should pull it. Now put yourself on a footbridge beside a large stranger. Pushing him onto the track would stop the trolley and save the five. Almost nobody says you should push.
Where the tram came from
The English philosopher Philippa Foot raised the question in 1967, inside an argument about abortion and the doctrine of double effect. Judith Jarvis Thomson named it “the trolley problem” in a 1976 article, and that article started a literature of its own. Later variants pushed the victim off bridges and harvested his organs for transplant patients.
The hard part was never the switch. It was explaining why the switch feels right when the footbridge and the transplant surgeon feel monstrous, although each trades one life for five. A Guardian essay notes that ethicists including Thomson spent decades trying to reconcile those verdicts.
The author who changed her mind
In a 2008 article Thomson questioned whether pulling the switch is right at all. She added a third option: you can steer the trolley into yourself. You are not obliged to give your own life. But if you would not, she argued, you cannot hand that death to a stranger on the side track. The essay reads her reversal as a case for a stronger reluctance to cause harm, not a weaker one.
Why it still gets used
The puzzle also turns up outside philosophy. At the US Military Academy at West Point, every cadet now studies philosophy and the trolley problem. Jeff McMahan of Rutgers University told the BBC that the case supports a distinction in international law. It separates targeting civilians from foreseeing civilian deaths as a side effect of an attack.
In 2016 Orin Kerr, a law professor at George Washington University, used the switch to frame a choice facing the FBI. Agents who seize a child abuse image site can shut it at once, or keep it running for a few days or weeks to identify its users. Kerr compared keeping it running to pulling the lever. The essay points to the fraud conviction of Sam Bankman-Fried, who said he was making money to give it away. The trolley problem, it argues, exists to investigate exactly his quandary: whether it is OK to cause harm for the greater good.
The case against it
Not every philosopher thinks the device helps. An essay in Aeon argues that such cases arrive stripped of context, far from the settings where people form their ethics. It reports that clinicians shown Thomson’s 1971 “violinist” case on abortion found it confusing, because they knew too much about real medicine.
The trolley has also escaped the seminar room. It has become an internet meme and a plot device in The Good Place.
