Joshua Greene

Joshua Greene brought trolley cases out of the seminar room and into the laboratory. His work in moral psychology, especially in the early 2000s, made trolley dilemmas central to experiments on judgment, emotion, and cognitive control. He did not invent the philosophical puzzle, but he changed its reach by suggesting that the difference between switching and pushing might reveal how the brain itself negotiates moral conflict.

Greene’s central question is empirical as well as philosophical: why do people judge some harm-based trade-offs in one way and structurally similar trade-offs in another? His influential "dual-process" approach proposes that certain judgments are driven by rapid emotional responses while others depend more on deliberate reasoning. Trolley cases are ideal for this framework because they reliably split intuitive responses. The switch case often feels permissible; the push case often does not.

The importance of Greene’s work lies in the translation of a thought experiment into a research program. Moral philosophy had long used cases to pressure theories; Greene showed that the same cases could illuminate the psychology of moral conflict. His broader project, culminating in work such as Moral Tribes, suggests that our moral systems evolved for small groups and now struggle under modern pluralism. The trolley problem becomes, in his hands, a clue to why morality is hard in large societies.

But Greene is also a figure of controversy. Critics worry that he moves too quickly from descriptive psychology to normative conclusions. If a judgment is emotional, it does not follow that it is irrational; if it is deliberative, it does not follow that it is correct. He is strongest when he presents his work as explanatory rather than as an all-purpose refutation of deontology.

His contradiction is productive: Greene is a philosopher-friendly empiricist who nonetheless tempts readers to think that neuroscience can settle ethics. The trolley problem remains a useful corrective to that temptation. It reminds us that learning how people judge is not the same as learning how they ought to judge.