“Right,” said the man, “please turn over the paper in front of you. You will see that there is a box for each of the questions you are about to encounter. Each question will give you the choice of pressing either the red or the black button. Please choose very carefully. Once you have chosen, write your reason in the box. Any questions? No? Good. Then we will begin.”

Wolf turned over the paper. It was thin and blue.

A picture came up on the screen. It was a shallow pond in what seemed to be a park. The pond had a small child in it. A voiceover explained that this child was in danger of drowning. “You are walking past the pond,” it said. “Do you help the child? There is no danger to your own life in doing so, but you may get slightly muddy. The red button is yes and the black button is no.”

Wolf reached for the red button. This was easy so far.

“Please fill in your reasons in the box,” said the voice.

Wolf didn’t much like tests, although he was strangely good at them in school. He also didn’t like writing a lot, so he tried to make his ideas as succinct as possible. Although this was hardly a difficult test. Who wouldn’t rescue a child from drowning? He wrote: It is my duty to save someone’s life if I can. Then he waited for the next part of the test. Around him, others were still writing. Wolf wondered what they were saying. Surely the answer was obvious? Maybe the participants were supposed to go into more detail about their reasons, but Wolf couldn’t think of anything to add that didn’t make him sound like a psycho. You rescue a child if you can, right? End of.

The screen went blank for a moment. All was quiet.

Then there was a scraping sound, as if someone was pushing back their chair in a hurry. But no one was pushing a chair back: One of the chairs was disappearing, down into the ground, so fast that the boy sitting on it didn’t have a chance to do anything about it. The last thing to go was his arm, as he reached for someone to help him.

So that was what it meant to be eliminated.

Wolf gulped.

The screen flickered as the projector brought up a new image. This time it was something that looked like a massive cigar in space. “There is a fifty percent chance that this object is a spaceship carrying alien life-forms,” said the voiceover. “There is a sixty percent chance that the aliens will be hostile. The object is heading for Earth. You have one chance to destroy it with a massive bomb. Press the red button now if you want to use your bomb. You only have ten seconds to decide. Ten, nine, eight, seven . . .”