Mirror Image (short story)

Plot summary

Daneel reaches out to Baley out of the blue about a mess on a spaceship. Two well-respected Spacers, both mathematicians, have turned in nearly identical papers on a groundbreaking mathematical method.

Each one says the other stole the idea after being asked for a simple opinion. Neither will confess, and the ship’s captain needs the dispute settled before they reach the planet where the papers are due, or his own reputation will suffer. Daneel, knowing Baley is an impartial outsider, recommends him to the captain.

Both Spacers own personal robots, identical models from the same production run, who were present during their discussions under matching conditions. But just like their owners, the robots give opposite accounts, perfectly mirroring each other. One robot must be truthful, the other lying to shield its master.

Because they are Spacers, the mathematicians refuse to talk directly to an Earthman, but they let Baley question their robots unofficially through a telepresence link. During the interviews, both robots admit they would lie to protect a human’s reputation. Baley then seizes on a crucial difference between the two men: one is old, near the end of a long, distinguished career, while the other is brilliant but not yet established.

Baley makes a different case to each robot. To the younger mathematician’s robot, he argues that its master could rebuild his name after a scandal, but an older man’s career would be permanently destroyed. To the elder mathematician’s robot, he says its master’s reputation is already secure, while the younger man’s career would be completely wrecked by early disgrace.

This psychological tactic works fast. The younger mathematician’s robot changes its story to protect the older man. The elder mathematician’s robot, caught in a conflict, malfunctions and shuts down.

Because Baley tried to persuade both robots to switch their accounts, he concludes the elder mathematician is the plagiarist. If the younger mathematician’s robot had not been ordered to lie, it could easily change sides. But if the elder mathematician’s robot had been told to lie and then felt it should tell the truth, it could not easily override its original directive on its own—especially when only a reputation, not a human life, was at stake—so it suffered an internal conflict and shut down.