Here's the scenario: a train is hurtling down a railway line, it's out of control and the brakes have failed. Ahead, five people are tied to the track - all five face certain death.

You can flick a switch to save them, but if you do another man has to die. What do you do?

Steve Evans explores the possible answers to this moral dilemma, to see what it tells us about the kind of ethical creatures humans are. Show less