A novice went into the master's cubicle and saw a new computer sitting upon the master's desk. "What is that computer?" asked the novice. The master placed his hand upon a small box that was connected to the computer by a wire. "Behold," said the master, "This device controls what we see on the screen." The novice looked closely at the screen, but all he saw were meaningless symbols. "The screen simulates a desk," explained the master. "For example, here on the screen is a filing cabinet and a trash repository. Here also is a typewriter and calculator." "This is a wonderful invention," whispered the novice in awe. "It is not as wonderful as it seems," said the master. He took the novice by the shoulders and made him stand several feet back. "Can you see the two desks?" asked the master. The novice nodded. "One is one the floor, the other is on the screen," he remarked. "Just so. Now, is there something missing on one of the two desks?" The novice pondered for a moment. "One of the desks does not have a computer on it," he said. The master shook his head. "Neither of the desks has a computer on it."