“Thou shalt not kill!” Imagine you are a train-yard operator who sees an out-of-control boxcar running down a track where five hikers are standing. The hikers won’t have time to get out of the way unless you flip a switch to change the car to another track. But on the second track there’s a worker repairing it. You have just seconds to make a decision: let the five hikers die — or kill the one worker. What do you do?