A runaway trolley, five people on the tracks, a lever, and one person on the sidetrack. This episode unpacks why a simple thought experiment breaks our brains, starting with the clash between utilitarian outcomes and deontological rules, the dirty hands problem, and the surprising origin of the dilemma in Philippa Foot's 1967 analysis of abortion ethics and the doctrine of double effect, with the name coined by Judith Jarvis Thomson in 1976 and precursors reaching back to a 1905 questionnaire and a 1954 television play.

We explore the fat man and fat villain variations, Joshua Greene's 2001 fMRI research showing emotional circuits hijack personal dilemmas, the role of serotonin, oxytocin and stress, the 90 percent who say they would pull the lever until a loved one is on the track, and the Vsauce simulation where five of seven participants  ...