Most people will pull a lever to save five lives — but not push someone to do it

In 1967, Philippa Foot asked whether it's permissible to divert a runaway trolley onto a track where it will kill one person instead of five. Almost everyone says yes. But change the scenario so you must push a bystander onto the tracks to physically stop the trolley, and most people refuse — even though the arithmetic is identical. The gap has driven decades of moral philosophy and neuroscience.

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