TrolleyProblem

The trolley problem is a thought experiment in normative ethics that presents a moral dilemma involving a runaway trolley. In its classic form, a trolley is speeding toward five people who are tied to a track and unable to move. A bystander can pull a lever to switch the trolley onto an alternate track, where one person is tied up. The question is whether it is permissible or obligatory to pull the lever, sacrificing one person to save five.

The problem was introduced by philosopher Philippa Foot in 1967 to explore the difference between acts and omissions in moral reasoning. It was later expanded by Judith Jarvis Thomson in 1976, who introduced variants such as the “fat man” version, where one must decide whether to push a large person onto the track to stop the trolley. The added scenarios emphasize tensions between consequentialist calculations and deontological intuitions about harming an innocent person.

Variations of the dilemma include different numbers of people on each track, a looping track that makes saving five possible only by sacrificing the one on the alternate path, and scenarios that involve direct physical contact with the person being sacrificed. These variants probe whether moral permissibility depends on whether one actively causes harm or merely allows it, and whether the decision aligns with utilitarian reasoning or adheres to moral rules.

The trolley problem has become central in discussions of ethics, moral psychology, and decision theory, illustrating how people balance outcomes against duties and rights, and it remains a focal point in debates about consequentialist versus deontological ethics.