“Maybe we should take the opportunity to start a balanced ecosystem here,” he said.

“Whatever for?” Avery asked, obviously shocked by the very idea.

“Well, Lucius was on the right track, in a way. Eventually there will be people living here, but a planet covered with nothing but people and robots and buildings and a few plants is going to be a pretty dull place. They’ll want birds and squirrels and deer and butterflies and-”

“What makes you think there are going to be people living here?”

It was Derec’s turn to be surprised. “Well, that’s the whole point, isn’t it? You didn’t design these robots to build city after city just for the heck of it. I know you said you did, but that was back when you-well, you know.”

“That was when I was crazy, you mean to say.” Derec blushed. “I forget; you don’t mince words. Okay, that was back when you were crazy. But now that you’re not any more, you can see that the robots eventually have to stop and serve, don’t you?”

“Why?”

“Why? You’re kidding. If you didn’t build all this for people to live in, then what do you intend to do with it?”

The truck slowed coming into an intersection, and another truck flashed by in front of them. Derec flinched, even though he knew the robot driver was aware of the other traffic in the area via comlink. Avery gave no indication that he had even seen the other truck. “I built it as an experiment,” he said. “I wanted to see what sort of society robots would come up with on their own. I also wanted to see if you were strong enough to take over the cities with the chemfets I implanted in your system.” When Derec began to speak, he raised his hand to cut him off and said, “I’ve already apologized for that, and I’ll do it again. That idea was the product of an insane mind. I had no right to do it, no matter how interesting the result. But the original idea was valid when I had it, and it’s still valid now. The cities exist for the robots. I want them to come up with their own society. I think there are basic rules for behavior among intelligent beings-rules that hold true no matter what their physical type-and I think robots can be used to discover those rules.”

For Avery to reveal anything of his plans to someone else, even to his own son, was a rare occurrence. Especially to his son. Avery had never confided any of his plans to Derec, had in fact used Derec at every turn as if he were just another robot. He had tried to make him a robot by injecting him with “chemfets,” modified copies of the cells that made up the Robot City robots. Derec had survived the infestation, had even arrived at a truce with the miniature robot city in his own body-that was how he had acquired his comlink-but he had not forgotten what his father had done to him. Forgiven, yes, but not forgotten.

Now suddenly Avery was confiding in him. Derec pondered this new development and its significance for the space of a couple of blocks before he said, “Well, they do seem to be working on it, but I’m not sure I see how anything you come up with from studying robots in a mutable city like this could apply to anything but more robots in an identical city.”

Avery nodded his head vigorously. “Oh, but it could. In fact, the city’s mutability forces the robots’ society to be independent of their environment. That’s the beauty of it. Any rules of behavior they come up with have to be absolute, because there’s no steady frame of reference for them to build upon.”

Derec wasn’t convinced, but he said, “So what are you going to do with these rules once you discover them?”

Avery smiled, another rare occurrence, and said, “That would have to depend on the rules, now wouldn’t it?”

Derec felt a chill run up his spine at those words. Ariel and the robots-and Avery himself-had sworn he was cured, but who could be sure? The human mind was still a poorly understood mechanism at best.

Derec had been to Dr. Avery’s laboratory once before, as a prisoner. Now, under better circumstances, he had the opportunity to gaze around him in wonder. Every instrument he could imagine-and some he couldn’t-for working on robots was there. Positronic circuit analyzers, logic probes, physical function testers, body fabrication machinery-the equipment went on and on. The laboratory would have been positively cluttered with it if it hadn’t been so large, but as it was it was simply well equipped. Derec would have bet it was the most advanced such lab anywhere, save that he and Avery were using it to explore the product of a still more advanced one somewhere else.

The three locked-up robots rested atop examining tables that, at first inspection, would have looked at home in a human hospital. A closer look, however, revealed that the pillows under the robots’ heads were not simple pillows but were instead inductive sensor arrays for reading the state of a positronic brain. Arm, leg, and body sheaths served a dual purpose: to restrain the patient if necessary and also to trace command impulses and sensory signals flowing to and from the extremities. Overhead stood scanning equipment that would allow the user to see inside a metal body.

There had been a moment of confusion when the cargo robots unloaded the three inert robots from the truck; without conscious control over their mutable shapes, they had all begun to drift back toward their primordial blank state. They had never been easy to identify, but now what few distinguishing features they had were smoothed out, melted. Even so, when viewed from a distance, one of them still seemed faintly wolflike in shape, and that had to be Adam. The “Kin,” the dominant life form on the world where he had first come to awareness, was a wolflike animal, and Adam’s first imprinting there had evidently become a permanent part of his cellular memory, however faint.

Likewise, Eve displayed just a hint of Ariel’s oval face, widely spaced eyes, and gently curvaceous female form, for it had been Ariel upon whom she had first imprinted.

Lucius, having hatched and imprinted in Robot City, still looked more like a robot than either of the others, and for that reason it was he whom Derec and Avery began examining first. Outward form probably didn’t mean that the inside would be anything like a normal robot’s, or even a normal Robot City robot’s, but there was at least a chance of it, and in any case they could learn more from studying a similar form rather than from something completely different.

The positronic brain, at least, was universal among robots of any manufacture, and despite Derec’s fear that this might be the exception that proved the rule, the pillow sensor fit itself around Lucius ‘ s head without complaint, the indicator light glowing green when the link with the brain had been established.

That alone told them something. Not all robots kept their brains in their heads; some models kept them inside the more protected chest cavity. Avery had designed his to function as much like humans as they could, which meant putting the brain in their heads so they would develop the same automatic responses concerning it. Injury-avoidance behavior, for instance, might be different in a being who kept its brain in a different part of its anatomy. To find the brains in the heads of these robots meant either that they were such excellent mimics that they could determine where their subject’s internal organs belonged, or that their creator was also concerned with the subtle differences the location of the brain might introduce into her robots’ behavior.

“Definitely getting mental activity,” Avery said, nodding toward the display screen upon which marched a series of square-edged waveforms. He tapped a button and a different series replaced the first. “Cognition appears undamaged,” he muttered, and switched the display again.

Derec suddenly felt a burst of recognition reach through the veil surrounding his past. There on the screen was the basic pattern common to all robots: the Three Laws graphically represented as pathway potentials within the positronic brain. He had learned that pattern years ago, probably in school, though just when it had been he couldn’t remember.