Dave hesitated, “As far as I know, nothing.”

“You didn’t produce any ore.”

“I know.”

“Well, then—”

Dave was having trouble, “I can’t explain that, boss. It’s been giving me a case of nerves, or it would if I let it. My subsidiaries worked smoothly. I know I did.” He considered, his photoelectric eyes glowing intensely. Then, “I don’t remember. The day ended and there was Mike and there were the ore cars, mostly empty.”

Donovan broke in, “You didn’t report at shift-end those days, Dave. You know that?”

“I know. But as to why—” He shook his head slowly and ponderously.

Powell had the queasy feeling that if the robot’s face were capable of expression, it would be one of pain and mortification. A robot, by its very nature, cannot bear to fail its function.

Donovan dragged his chair up to Powell’s desk and leaned over, “Amnesia, do you think?”

“Can’t say. But there’s no use in trying to pin disease names on this. Human disorders apply to robots only as romantic analogies. They’re no help to robotic engineering.” He scratched his neck, “I hate to put him through the elementary brain-reaction tests. It won’t help his self-respect any.”

He looked at Dave thoughtfully and then at the Field-Test outline given in the “Handbook.” He said, “See here, Dave, what about sitting through a test? It would be the wise thing to do.”

The robot rose, “If you say so, boss.” There was pain in his voice.

It started simply enough. Robot DV-5 multiplied five-place figures to the heartless ticking of a stop watch. He recited the prime numbers between a thousand and ten thousand. He extracted cube roots and integrated functions of varying complexity. He went through mechanical reactions in order of increasing difficulty. And, finally, worked his precise mechanical mind over the highest function of the robot world—the solutions of problems in judgment and ethics.

At the end of two hours, Powell was copiously besweated. Donovan had enjoyed a none-too-nutritious diet of fingernail and the robot said, “How does it look, boss?”

Powell said, “I’ve got to think it over, Dave. Snap judgments won’t help much. Suppose you go back to the C-shift. Take it easy. Don’t press too hard for quota just for a while—and we’ll fix things up.”

The robot left. Donovan looked at Powell.

“Well—”

Powell seemed determined to push up his mustache by the roots. He said, “There is nothing wrong with the currents of his positronic brain.”

“I’d hate to be that certain.”

“Oh, Jupiter, Mike! The brain is the surest part of a robot. It’s quintuple-checked back on Earth. If they pass the field test perfectly, the way Dave did, there just isn’t a chance of brain misfunction. That test covered every key path in the brain.”

“So where are we?”

“Don’t rush me. Let me work this out. There’s still the possibility of a mechanical breakdown in the body. That leaves about fifteen hundred condensers, twenty thousand individual electric circuits, five hundred vacuum cells, a thousand relays, and umpty-ump thousand other individual pieces of complexity that can be wrong. And these mysterious positronic fields no one knows anything about.”