In my education classes, I often start off by asking students to state what they would consider to be the highest, most moral act. Invariably, students propose risking one's life to save the life of another as the most moral thing a person could do. I then present them with the following scenario and ask whether it is similar to what they had in mind.

A man is waiting at a train station. On his right, about twenty feet away, stands a woman reading a magazine. The man glances to his left to check if a train is coming and sees to his horror that another man, about twenty feet from him, is in a crouched position clearly aiming a gun at the woman. The man is too far away to either push the woman or stop the shooter. So he yells out “duck” as he steps between the shooter and the woman just as the gun is fired. As a result, the bullet intended for the woman strikes him in the arm, saving the woman's life.

Generally, my students accept this scenario as a rather dramatic instance of what they had in mind. I then ask them to consider the following alternative scene.

The same people are on the train platform in the same relative positions as in the first version. However, the man in the middle is in this case unaware of the presence of the gunman. While waiting for the train, he notices that his shoe is untied. Just at the moment that our “hero” bends forward to tie his shoe, the gunman fires at the woman.