The Trolley Problem: One to Save Five?
Foot 1967 → Greene 2001 — morality in two brain systems
Two Scenarios
The "Trolley Problem" first appeared in Philippa Foot's 1967 paper, "The Problem of Abortion and the Doctrine of the Double Effect." Initially conceived as a thought experiment to analyze the ethics of abortion, it was later developed by philosopher Judith Jarvis Thomson in 1976, who clarified its two distinct versions. **Version 1 (The Lever):** A runaway trolley is headed towards five people. If you pull a lever, it will divert to another track, killing one person instead. **Version 2 (The Bridge):** You are standing on a bridge overlooking the tracks. To stop the trolley from hitting five people, you must push a large person off the bridge onto the tracks below. Mathematically, both scenarios involve the same outcome: sacrificing one life to save five. However, our intuitive responses to them often differ significantly.
Two Brain Systems
In 2001, Joshua Greene conducted an fMRI study titled "An fMRI Investigation of Emotional Engagement in Moral Judgment." Participants' brains were scanned as they considered the two trolley scenarios. The results showed distinct patterns of neural activity. In the **lever scenario**, the dorsolateral prefrontal cortex (DLPFC), associated with reasoning, showed increased activation. Conversely, the **bridge scenario** activated the medial prefrontal cortex (mPFC) and the amygdala, regions linked to emotion. A small number of participants who decided it was "right" to push the person off the bridge took, on average, longer to make their decision and exhibited signs of cognitive conflict. This suggests that morality isn't a singular rational calculation, but rather a conflict between Kahneman's System 1 (fast, emotional processing) and System 2 (slower, deliberate reasoning). Greene termed this the "dual-process model of morality."
Autonomous Cars and the Trolley Problem
In the 2010s, the abstract trolley problem suddenly became a practical concern with the advent of autonomous vehicles. MIT's "Moral Machine" online experiment, launched in 2018, engaged 2.3 million participants worldwide. It presented scenarios where a self-driving car faced an unavoidable accident, forcing a choice: who should be protected? The dilemmas included adults versus children, humans versus animals, and law-abiding pedestrians versus jaywalkers. The results revealed that **answers varied significantly by culture.** Western countries tended to prioritize younger individuals, while East Asian cultures often favored the elderly. Latin American participants, on the other hand, frequently prioritized women. This global experiment underscored that morality is not a universal constant but is deeply embedded within cultural contexts. To this day, developers of autonomous vehicles continue to grapple with these complex ethical dilemmas, unable to provide a definitive "right" answer.
The Character 善 (Seon)
The Chinese character for "good," **善 (Seon)**, offers a profound insight into this complexity. It is composed of two radicals: 羊 (yang), meaning "sheep," and 言 (eon), meaning "speech" or "words." This combination suggests "words that come from a gentle mouth, like a sheep," signifying good words or righteousness. The classical text "The Great Learning" states, "止於至善" (Jieo Ji Seon), which translates to "to rest in the highest good." The trolley problem forces us to question: Is sacrificing one life to save five the "highest good"? Is pushing one person for the sake of five others? The very nature of the trolley problem demonstrates that "good" is not a singular, straightforward answer. The ancient character 善, with its blend of the sheep's gentleness and the truthfulness of speech, encapsulates the dual aspects of morality—both reasoning and emotion. This intricate understanding has been condensed within a single character for over 2,500 years.
