Five or One? The Trolley Problem That Divides the World

Key takeaways

• In an online survey of about 5,000 people from more than 100 countries, about 9 in 10 said pulling the lever to save five is acceptable, but only about 1 in 10 said pushing a man off a footbridge is acceptable, even though the numbers are the same.
• The question began with Philippa Foot at Oxford in 1967, as a tram driver choosing between tracks. Judith Jarvis Thomson named it 'the trolley problem' in 1976, added the footbridge, put a bystander at the switch in 1985, and changed her own answer in 2008.
• Joshua Greene's small 2001 brain-scan study (9 people per experiment) found that 'personal' dilemmas like the footbridge engage emotion-related brain areas more, while 'impersonal' ones like the lever engage areas for reasoning and calculation.
• Bentham and Mill say do the most good for the most people; Kant says never use a person merely as a tool. Aquinas' double effect and the Buddha's teaching that intention is karma (AN 6.63) point to the difference between a death you foresee and a death you aim at.
• MIT's Moral Machine gathered nearly 40 million decisions from 233 countries and territories (Nature, 2018): people everywhere tend to spare humans over animals, more lives over fewer and the young over the old, though the preference for the young is weaker in the Eastern cluster. Not choosing is also a choice.