McGuire was different. In the first place, he was mobile. He was in command of a spacecraft. In a sense, he _was_ the spacecraft, since it served him in a way that was analogous to the way a human body serves the human mind. And he wasn't in charge of millions of objects with a top velocity of a hundred and fifty miles an hour; he was in charge of a single object that moved at velocities of thousands of miles per second. Nor did he have a set, unmoving highway as his path; his paths were variable and led through the emptiness of space. Unforeseen emergencies can happen at any time in space, most of them having to do with the lives of passengers. A cargo ship would be somewhat less susceptible to such emergencies if there were no humans aboard; it doesn't matter much to a robot if he has no air in his hull. But with passengers aboard, there may be times when it would be necessary to give orders--_fast_! And that means verbal orders, orders that can be given anywhere in the ship and relayed immediately by microphone to the robot's brain. A man doesn't have time to run to a teletyper and type out orders when there's an emergency in space. That meant that McGuire had to understand English, and, since there has to be feedback in communication, he had to be able to speak it as well. And that made McGuire more than somewhat difficult to deal with. * * * * * For more than a century, robotocists have been trying to build Asimov's famous Three Laws of Robotics into a robot brain. _First Law: A robot shall not, either through action or inaction, allow harm to come to a human being._ _Second Law: A robot shall obey the orders of a human being, except when such orders conflict with the First Law_. _Third Law: A robot shall strive to protect its own existence, except when this conflicts with the First or Second Law._ Nobody has succeeded yet, because nobody has yet succeeded in defining the term "human being" in such a way that the logical mind of a robot can encompass the concept. A traffic robot is useful only because the definition has been rigidly narrowed down. As far as a traffic robot is concerned, "human beings" are the automobiles on its highways. Woe betide any poor sap who tries, illegally, to cross a robot-controlled highway on foot. The robot's only concern would be with the safety of the automobiles, and if the only way to avoid destruction of an automobile were to be by nudging the pedestrian aside with a fender, that's what would happen. And, since its orders only come from one place, I suppose that a traffic robot thinks that the guy who uses that typer is an automobile. With the first six models of the McGuire ships, the robotocists attempted to build in the Three Laws exactly as stated. And the first six went insane.