A famous thought experiment in ethics where a runaway trolley will kill five people unless you divert it to kill one person instead. It explores the distinction between killing and letting die, and between intended and merely foreseen consequences.
Created by philosopher Philippa Foot in 1967 and developed by Judith Jarvis Thomson. The problem became central to moral philosophy and psychology, spawning numerous variations that test moral intuitions about permissible harm.
This deceptively simple scenario has launched thousands of philosophical papers and reveals deep inconsistencies in our moral thinking — most people say it's okay to flip a switch to divert the trolley but not okay to push a large person off a bridge to stop it, even though both save five lives by sacrificing one!
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