You see a runaway railway trolley about to careen through a tunnel: five people in the tunnel will not be able to escape in time and will surely be killed. But then you see a switch that would divert the trolley into a different tunnel. Unfortunately there is somebody in there too, who will be killed if you divert the trolley. What do you do? Do you flip the switch and kill one person to save five?
This is the Trolley Problem, first posed by the British philosopher Philippa Foot a few decades ago. Since then, countless variations have been proposed, with different conditions and tradeoffs. These situations are quite artificial, but still important. They can be used as thinking exercises to help understand how to make ethical decisions in real life. For example, is it right to torture a suspected terrorist if you think you might get information that could save a hundred people from being killed by a bomb?
This book is a very entertaining and thought-provoking survey of the trolley problem and its many variants. There is a lot in it. While reading it I kept thinking, “Yes, but what about…” only to turn the page and see that very point addressed. It’s not often I have read such a thorough book that is also so light-hearted and fun.