The transplant
Judith Jarvis Thomson, “Killing, Letting Die, and the Trolley Problem,” The Monist (1976), as a contrast with the tram.
The transplant case is used because many people who would divert the tram would not harvest the organs. If both are “one death against five,” the difference has to be stated. Thomson’s discussion is part of that effort. The difference might be about rights, about using a person, about doing and allowing, or about something the numbers do not capture.
On this site the case bears on both the moral axis and the social axis, because it is at once a question about outcomes and a question about whether one person is a limit. It is not a prompt for medical advice.