Imagine yourself to be a surgeon, a truly great surgeon. Among other things you do, you transplant organs, and you are such a great surgeon that the organs you transplant always take. At the moment, you have five patients who need organs. Two need one lung each, two need a kidney each, and the fifth needs a heart. If they do not get those organs today, they will all die; if you find organs for them today, you can transplant the organs and they will all live. But where to find the lungs, the kidneys, and the heart? The time is almost up when a report is brought to you that a young man who has just come into your clinic for his yearly check-up has exactly the right blood-type and is in excellent health. Lo, you have a possible donor. All you need to do is cut him up and distribute his parts among the five who need them. You ask, but he says, ‘Sorry. I deeply sympathize, but no.’ Would it be morally permissible for you to operate anyway?

— Judith Jarvis Thompson, “The Trolley Problem,” Yale Law Journal, 1985