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.

If one human being says "jump left," and another says "jump right," the robot is unable to evaluate which human being has given the more valid order. Feed enough confusing and conflicting data into a robot brain, and it can begin behaving in ways that, in a human being, would be called paranoia or schizophrenia or catatonia or what-have-you, depending on the symptoms. And an insane robot is fully as dangerous as an insane human being controlling the same mechanical equipment, if not more so.

So the seventh model had been modified. The present McGuire's brain was impressed with slight modifications of the First and Second Laws.

If it is difficult to define a human being, it is much more difficult to define a responsible human being. One, in other words, who can be relied upon to give wise and proper orders to a robot, who can be relied upon not to drive the robot insane.

The robotocists at Viking Spacecraft had decided to take another tack. "Very well," they'd said, "if we can't define all the members of a group, we can certainly define an individual. We'll pick one responsible person and build McGuire so that he will take orders only from that person."

As it turned out, I was that person. Just substitute "Daniel Oak" for "human being" in the First and Second Laws, and you'll see how important I was to a certain spaceship named McGuire.

When I finally caught the beam from Ceres and set my flitterboat down on the huge landing field that had been carved from the nickel-iron of the asteroid with a focused sun beam, I was itchy with my own perspiration and groggy tired. I don't like riding in flitterboats, sitting on a bucket seat, astride the drive tube, like a witch on a broomstick, with nothing but a near-invisible transite hull between me and the stars, all cooped up in a vac suit. Unlike driving a car, you can't pull a flitterboat over and take a nap; you have to wait until you hit the next beacon station.

Ceres, the biggest rock in the Belt, is a lot more than just a beacon station. Like Eros and a few others, it's a city in its own right. And except for the Government Reservation, Viking Spacecraft owned Ceres, lock, stock, and mining rights.

Part of the reason for Viking's troubles was envy of that ownership. There were other companies in the Belt that would like to get their hands on that plum, and there were those who were doing everything short of cutting throats to get it. The PSD was afraid it might come to that, too, before very long.

Ceres is fifty-eight million cubic miles of nickel-iron, but nobody would cut her up for that. Nickel-iron is almost exactly as cheap as dirt on Earth, and, considering shipping costs, Earth soil costs a great deal more than nickel-iron in the Belt.

But, as an operations base, Ceres is second to none. Its surface gravity averages .0294 Standard Gee, as compared with Earth's .981, and that's enough to give a slight feeling of weight without unduly hampering the body with too much load. I weigh just under six pounds on Ceres, and after I've been there a while, going back to Earth is a strain that takes a week to get used to. Kids that are brought up in the Belt are forced to exercise in a room with a one-gee spin on it at least an hour a day. They don't like it at first, but it keeps them from growing up with the strength of mice. And an adult with any sense takes a spin now and then, too. Traveling in a flitterboat will give you a one-gee pull, all right, but you don't get much exercise.

I parked my flitterboat in the space that had been assigned to me by Landing Control, and went over to the nearest air-lock dome.

After I'd cycled through and had shucked my vac suit, I went into the inner room to find Colonel Brock waiting for me.

"Have a good trip, Oak?" he asked, trying to put a smile on his scarred, battered face.

"I got here alive, if that makes it a good flitterboat trip," I said, shaking his extended hand.

"That's the definition of a good trip," he told me.

"Then the question was superfluous. Seriously, what I need is a bath and some sleep."

"You'll get that, but first let's go somewhere where we can talk. Want a drink?"

"I could use one, I guess. Your treat?"

"My treat," he said. "Come on."

I followed him out and down a ladder to a corridor that led north. By definition, any asteroid spins toward the east, and all directions follow from that, regardless of which way the axis may point.

Colonel Harrington Brock was dressed in the black-and-gold "union suit" that was the uniform of Ravenhurst's Security Guard. My own was a tasteful green, but some of the other people in the public corridor seemed to go for more flashiness; besides silver and gold, there were shocking pinks and violent mauves, with stripes and blazes of other colors.

A crowd wearing skin-tight cover-alls might shock the gentle people of Midwich-on-the-Moor, England, but they are normal dress in the Belt. You can't climb into a vac suit with bulky clothing on, and, if you did, you'd hate yourself within an hour, with a curse for every wrinkle that chafed your skin. And, in the Belt, you never know when you might have to get into a vac suit fast. In a "safe" area like the tunnels inside Ceres, there isn't much chance of losing air, but there are places where no one but a fool would ever be more than ten seconds away from his vac suit.

I read an article by a psychologist a few months back, in which he claimed that the taste for loud colors in union suits was actually due to modesty. He claimed that the bright