A trolley is careering out of control. Up ahead are five workers; on a spur to the right stands a lone individual. You, a bystander, happen to be standing next to a switch that could divert the trolley, which would save the five, but sacrifice the one—do you pull it? Or say you’re watching from an overpass. The only way to save the workers is to drop a heavy object in the trolley’s path. And you’re standing next to a really fat man….

This ethical conundrum—based on British philosopher Philippa Foot’s 1967 thought experiment—has inspired decades of lively argument around the world. Now Thomas Cathcart, coauthor of the New York Times bestseller Plato and a Platypus Walk into a Bar, brings his sharp intelligence, quirky humor, and gift for popularizing serious ideas to “the trolley problem.” Framing the issue as a possible crime that is to be tried in the Court of Public Opinion, Cathcart explores philosophy and ethics, intuition and logic. Along the way he makes connections to the Utilitarianism of Jeremy Bentham, Kant’s limits of reason, St. Thomas Aquinas’s fascinating Principle of Double Effect, and more.

Read with an open mind, this provocative book will challenge your deepest held notions of right and wrong. Would you divert the trolley? Kill one to save five? Would you throw the fat man off the bridge?

Thomas Cathcart graduated from Harvard with a degree in philosophy, studied theology at the University of Chicago, and embarked on a “checkered career” (his words) from college teaching to hospice management until, at the age of 67, he started his writing life by coauthoring Plato and a Platypus Walk into a Bar with Daniel Klein. Mr. Cathcart and his wife live in New York City.