Stephen Byerley is a lawyer with political ambitions. In his current campaign, however, an interesting bit of dirt is being tossed about—that he isn’t a human being at all, but a robot, and U.S. Robots and the great Susan Calvin have been enlisted to prove the matter one way or the other. Byerley refuses, however, to cooperate and the matter is left hanging until just before the election, when in a dramatic gesture, Byerley proves his humanity by striking a human being. In retrospect, however, Calvin realizes that the whole thing may have been a set-up, that the human struck might have been another robot, and that Byerley might be a robot after all.

A terrific story. Perhaps the very best Susan Calvin story of all. The situation is dramatic, the answer never revealed until the very end, the characters solid. More to the point, however, we get here a very explicit acknowledgement of a basic philosophy Asimov held regarding the Three Laws (a point which is underscored by the bracketing material in I, Robot): the Three Laws are laws of ethics, laws that human beings might be well to emulate, and laws which robots cannot break by their very nature—while human beings can.

This is definitely one of the key stories for anybody interested in Asimov’s robots to read.