During a simulated attack, the troops have to defend themselves against an imaginary enemy, as the sergeant calls it. Bawling out orders, he notices that one recruit shows little response.
“You there,” the sergeant shouts, “the imaginary enemy is advancing, and your are caught in the crossfire. Action!”
The recruit takes ten steps to one side.
“What are you doing, man?” Yells the sergeant, purple with fury.
“I’m taking shelter behind an imaginary hill, Sergeant,” answers the recruit calmly.