Would you kill one person to save five? Most say yes — until they have to push

Philippa Foot's thought experiment asks whether it's right to divert a runaway trolley onto a track where it kills one person instead of five. Most people say yes. But flip it slightly — push one large man off a bridge to block the trolley, same numbers — and most people refuse. The outcome is identical; only the method of causing it changes our answer.

— Philippa Foot, The Problem of Abortion and the Doctrine of Double Effect — Oxford Review, 1967