IT WAS LIKE being constructed allover again. For days, for weeks, for months, Andrew found himself not himself somehow, and the simplest actions kept giving rise to hesitation.

He had always been utterly at home in his body. He had only to recognize the need for a motion and he was instantly able to make that motion, smoothly, automatically. Now it took a conscious effort of self-direction. Raise your arm, he had to tell himself. Move it over here. Now put it down.

Was this what it was like for a young human child as it strived to master the mysteries of bodily coordination? Andrew wondered.

Perhaps so. He was over a hundred years old and yet he felt very much like a child as he moved about in this startling new body of his.

It was a splendid body. They had made him tall, but not so tall that he would seem overbearing or frightening. His shoulders were broad, his waist was slim, his limbs were supple and athletic. He had chosen light-brown hair for himself, since he found red too flamboyant and yellow too obvious and black too somber, and human hair did not seem to come in other colors than those, except for the gray or white or silver of age, and he had not wanted that. His eyes-photo-optic cells, really, but very convincing in appearance-were brown also, flecked ever so subtly with gold. For his skin color Andrew had selected something neutral in tone, a kind of blend of the prevailing skin colors of the various human types, darker than the pale pink of the Charneys but not quite as dark as some. That way no one would be able to tell at a glance which race he belonged to, since in fact he belonged to none. He had had the U. S. Robots designers peg his apparent age at somewhere between thirty-five and fifty human years: old enough to seem mature, not so old as to show serious signs of aging.

A fine body, yes. He was certain he would be very happy in it, once he grew accustomed to it.

Each day there was a little progress. Each day he gained more control over his elegant new android housing. But the process was terribly slow -agonizingly slow

Paul was frantic. "They've damaged you, Andrew. I'm going to have to file suit."

Andrew said, "You mustn't, Paul. You'll never be able to prove something-m-m-m-m- "Malicious?"

"Malicious, yes. Besides, I grow stronger, better. It's just the tr-tr-"

"Tremble?"

"Trauma. After all, there's never been such an op-op-op-before."

Andrew spoke very slowly. Speech was surprisingly hard now for him too, one of the hardest functions of all, a constant struggle to enunciate. It was an agony for Andrew to get the words out and an agony for anyone who had to listen to him. His entire vocal mechanism was different from what it had been previously. The efficient electronic synthesizer that had been able to make such convincingly human sounds had given way to an arrangement of resonating chambers and muscle-like structures to control them that was supposed to make his voice utterly indistinguishable from that of an organic human being; but now Andrew had to shape each syllable in a way that had been done for him before, and that was difficult work, very difficult.

Yet he felt no despair. Despair was not really a quality that he was capable of, and in any case he knew that these problems were merely temporary. He could feel his brain from the inside. No one else could; and no one else could know as well as he did that his brain was still intact, that it had come through the transfer operation unharmed. His thoughts flowed freely through the neural connections of his new body, even if the body was not yet as swift as it might be in reacting to them. Every parameter checked out perfectly.

He was merely having a few interface problems, that was all. But Andrew knew he was fundamentally well and that it would be only a matter of time until he had achieved complete control over his new housing. He had to think of himself as very young, still. Like a child, a newborn child.

The months passed. His coordination improved steadily. He moved swiftly toward full positronic interplay.

Yet not everything was as he would have wished it. Andrew spent hours before the mirror, evaluating himself as he went through his repertoire of facial expressions and bodily motions. And what he saw fell far short of the expectations he had had for his new body.

Not quite human! The face was stiff-too stiff-and he doubted that that was going to improve with time. He would press his finger against his cheek and the flesh would yield, but not in the way that true human flesh would yield. He could smile or scowl or frown, but they were studied, imitative smiles and scowls and frowns. He would give the smile-signal or the frown-signal or whatever, and the muscles of his face would obediently hoist the smile-expression or the frown-expression into view, pulling his features around in accordance with a carefully designed program. He was always conscious of the machinery, organic though it might be, clanking ponderously around beneath his skin to produce the desired effect. That was not how it happened with human beings, Andrew suspected.

And his motions were too deliberate. They lacked the careless free flow of the human being. He could hope that that would come after a while-he was already far beyond the first dismal days after the operation, when he had staggered awkwardly about his room like some sort of crude pre-positronic automaton-but something told him that even with this extraordinary new body he was never going to be able to move in the natural way that virtually every human being took for granted.

Still, things were not all that bad. The U. S. Robots people had kept their part of the bargain honorably and had carried out the transfer with all the formidable technical skill at their disposal. And Andrew had what he wanted. He might not fool the truly observant onlooker into thinking he was human, but he was far more human-looking than any robot ever had been, and at least he could wear clothes now without the ridiculous anomaly of an expressionless metal face rising up above them.

Eventually Andrew declared, "I will be getting back to work now."

Paul Charney laughed and said, "Then you must be well. What will you be doing? Another book?"

"No," said Andrew seriously. "I live too long for anyone career to seize me by the throat and never let me go. There was a time when I was primarily an artist, and I still dabble in that now and then. And there was a time when I was a historian and I can always write another book or two, if I feel the need for it. But I have to keep moving on. What I want to be now, Paul, is a robobiologist."

"A robopsychologist, you mean?"

"No. That would imply the study of positronic brains and at the moment I have no interest in doing that. A robobiologist, it seems to me, would be concerned with the workings of the body that is attached to that brain."

"Wouldn't that be a roboticist?"

"In the old days, yes. But roboticists work with metallic bodies. I would be studying an organic humanoid body-of which I have the only one, as far as I know. Examining the way it functions, the way it simulates a true human body. I want to know more about artificial human bodies than the android-makers know themselves."

"You narrow your field of endeavor," said Paul thoughtfully. "As an artist, the whole range of expression was yours. Your work could stand up with the best that was being produced anywhere in the world. As a historian, you dealt chiefly with robots. As a robobiologist, your subject will be yourself."

Andrew nodded. "So it would seem."

"Do you really want to turn inward that way?"

"Understanding of self is the beginning of understanding of the entire universe," said Andrew. "Or so I believe now. A newborn child thinks he is the whole universe, but he is wrong, as he soon begins to discover. So he must study what is outside himself-must try to learn where the boundaries are between himself and the rest of the world-in order to arrive at any comprehension of who he is and how he is to conduct his life. And in many ways I am like a newborn child now, Paul. I have been something else before this, something mechanical and relatively easy to understand, but now I am a positronic brain within a body that is almost human, and I can barely begin to comprehend myself. I am alone in the world, you know. There is nothing like me. There never has been. As I move through the world of humans, no one will understand what I am, and I barely understand it myself. So I must learn. If that is what you call turning inward, Paul, so be it. But it is the thing that I must do."

Andrew had to start from the very beginning, for he knew nothing of ordinary biology, almost nothing of any branch of science other than robotics. The nature of organic life, the chemical and electrical basis of it, was a mystery to him. He had never had any particular reason to study it before. But now that he was organic himself-or his body was, at any rate-he experienced a powerful need to expand his knowledge of living things. To understand how the designers of his android body had been able to emulate the workings of the human form, he needed first to know how the genuine article functioned.

He became a familiar sight in the libraries of universities and medical schools, where he would sit at the electronic indices for hours at a time. He looked perfectly normal in clothes and his presence caused no stir whatever. Those few who knew that he was a robot made no attempt to interfere with him.

He added a spacious room to his house to serve as a laboratory, and equipped it with an elaborate array of scientific instruments. His library grew, too. He set up research projects for himself that occupied him for weeks on end of his sleepless twenty-four-hour-a-day days. For sleep was still something for which Andrew had no need. Though virtually human in outer appearance, he had been given ways of restoring and replenishing his strength that were far more efficient than those of the species after which he had been patterned.

The mysteries of respiration and digestion and metabolism and cell division and blood circulation and body temperature, the whole complex and wondrous system of bodily homeostasis that kept human beings functioning for eighty or ninety or, increasingly, even a hundred years, ceased to be mysteries to him. He delved deep into the mechanisms of the human body-for Andrew saw that that was every bit as much a mechanism as were the products of U. S. Robots and Mechanical Men. It was an organic mechanism, yes-but a mechanism nevertheless, a beautifully designed one, with its own firm laws of metabolic rhythm, of balance and decay, of breakdown and repair.

Years went by, quiet ones not only within Andrew's secluded retreat on the grounds of the old Martin estate, but in the world outside. The Earth's population was stable, held level not only by a low birth rate but by steady emigration to the growing settlements in space. Giant computers controlled most economic fluctuations, keeping supply and demand in balance between one Region and another so that the ancient business cycles of boom and bust were flattened into gentle curves. It was not a challenging, dynamic era; but it was not a turbulent or perilous one, either.

Andrew paid next to no attention to developments that might be going on beyond his doorstep. There were more fundamental things that he needed and wanted to explore, and he was exploring them. That was all that mattered to him these days. His income, which came from the invested proceeds of his now terminated career as an artist in wood and from the money that Little Miss had left him, was more than sufficient to take care of his bodily-maintenance needs and to cover the costs of his research.

It was a private, hermetic life: precisely what he wanted. He had long since gained complete mastery over his android body, after the awkward early days, and often he took long walks through the forest atop the bluff, or along the lonely, tempestuous beach where once he had gone with Little Miss and her sister. Sometimes he went swimming-the iciness of the water was no problem for him-and even occasionally risked the journey out to the isolated, forlorn cormorant rock that Miss had asked him to undertake when she was a child. It was a difficult swim even for him, and the cormorants did not seem to enjoy his company. But he enjoyed testing his strength against such a challenge, aware that no human, even the strongest of swimmers, could safely manage the trip out and back through that chilly, violent sea.

Much of the time, though, Andrew spent at his research. There were frequent periods when he did not go out of his house for weeks on end.

Then Paul Charney came to him one day and said, "It's been a long time, Andrew."

"Indeed it has." They rarely saw each other now, though there had been no estrangement of any sort. The Charney family still maintained its home along the upper coast of Northern California, but Paul had taken to spending most of his time nearer to San Francisco.

"Are you still deep in your program of 'biological research?" Paul asked.

"Very much so," Andrew said.

He was startled by how much Paul had aged. The phenomenon of human aging was something that Andrew had been studying lately with particular interest, and he thought he had arrived at some understanding of its causes and its processes. And yet-for all his experience of age in the generations of this one family, from Sir down through Little Miss to George and now to Paul-it always came as a surprise to him that humans so swiftly grew gray and withered and bent and old. As Paul had done. His long-limbed frame seemed shorter now, and his shoulders were slumped, and the bony structure of his face had undergone subtle changes so that his chin had begun to jut and his cheekbones were less prominent. His eyesight, too, must have suffered, for his eyes had been replaced with gleaming photo-optic cells much like the ones by which Andrew viewed the world. So he and Paul had grown closer in that one respect, at least.

Paul said, "It's a pity you're no longer as concerned as you once were with the history of robots. Your book would need a new chapter, now."

"What do you mean, Paul?"

"A chapter that deals with the radical new policy that U. S. Robots has established."

"I know nothing about that. What new policy are you referring to?"

Paul's eyebrows lifted. "You haven't heard? Really? -Well, Andrew, what they have done is to begin manufacturing central control stations for their robots-giant positronic computers, actually, which are able to communicate with anywhere from a dozen to a thousand robots by microwave transmission. The robots they're turning out now have no brains at all."

"No brains? But how do they-"

"The gigantic central brains do all the data-processing for them. The robot units themselves are nothing more than mobile limbs of the main thinking center."

"Is that more efficient?"

"U. S. Robots insists that it is. Whether it really is, I can't say. But it's my notion that the whole thing is mainly a long-range way of getting back at you. Smythe-Robertson authorized the turn toward the new direction just before he died, you see. He was old and ill, but he pushed his program through and made it stick. And I suspect that what he wanted was to make certain that the company would never again be confronted by a robot able to give them all the trouble that you have. So they've begun to separate brain and body. A mindless mechanical laboring unit can't be deemed worthy of civil rights or legislative protection; and a big brain that sits in a box is just a computer. The brain isn't going to be able to turn up in the office of the Chairman of the Board one day and demand to be put into a fancy new body. And the robot bodies, since they're completely brainless, aren't in a position to conceive any demands at all."

"It seems like a long step backward," Andrew said. "They've undone two hundred years of progress in robotics merely to spare themselves some small degree of political trouble."

"Indeed. Indeed." Paul smiled and slowly shook his head. "It's astonishing, Andrew, the influence you have had on the history of robotics. It was your artistry that encouraged U. S. Robots to make more robots more precise and specialized, because you seemed too clever by half, and they were afraid that that would frighten people. It was your winning your freedom that resulted in the establishment of the principle of robot rights. And it was your insistence on having an android body that made U. S. Robots switch over to this brain-body separation."

Andrew said, "I suppose in the end what the corporation will have created is a world that has just one vast brain controlling several billion robot bodies. All the eggs will be in one basket, then. Dangerous. Not in any way sensible."

"I think you're right," said Paul. "But I don't suspect it will come to pass for a century, at least. Which means I won't be here to see it."

He had crossed the room, and stood by the open doorway, looking out into the wooded grove just beyond. A mild moist spring breeze was blowing from the ocean, and Paul inhaled deeply as though trying to drink it in. After a moment he turned to face Andrew, and he seemed suddenly to have grown ten years older in just the time that he had been here.

"In fact," Paul said in a voice that was no more than a husk of itself, "I may not live to see next year."

"Paul!"

"Don't sound so surprised. We're mortal, Andrew," Paul said, with a shrug. "We're not like you, and by this time you ought to understand what that means."

"I do. But-"

"Yes. Yes, I know. I'm sorry, Andrew. I know how devoted you've been to our family, and what a sad and dreary thing it must be for you constantly to see us growing up and getting older and older and eventually dying. Well, we don't like it much either, I have to tell you, but there's no sense railing against it. We live twice as long as human beings usually did just a few hundred years ago. That's long enough for most of us, I suppose. We simply have to be philosophical about it."

"But I don't understand. How can you be so calm in the face of-of complete termination? Of the total end of all your striving, all your desire to achieve and learn and grow?"

"I wouldn't be, I suppose, if I were twenty years old right now, or even forty. But I'm not. And part of the system, Andrew-the good part, I guess-is that when you reach a certain age it generally stops mattering to you so much that you're inevitably going to die soon. You aren't really achieving and learning and growing any more. For better or for worse, you've lived your life and done whatever you can for the world and for yourself, and now your time is up and your body knows that and accepts it. We get very tired, Andrew. You don't know what that word means, not really, do you? No. No, I see that you don't. You can't. You aren't able to get tired and so you have only a theoretical knowledge of what it's like. But it's different for us. We slog on and on for seventy or eighty or maybe a hundred years and eventually it all just becomes too much, and so we sit down and then we lie down and finally we close our eyes and don't open them again, and right at the end we know that it is the end and we simply don't mind. Or don't care: I'm not sure that's the same thing, really, but perhaps it is. -Don't look at me that way, Andrew."

"Dying is a natural thing for humans," Andrew said. "I do understand that, Paul."

"No. You don't. You really don't. It just isn't possible for you to understand. You secretly think that death is some sort of lamentable design flaw in us and you can't understand why it hasn't been fixed, because it ought to be pretty simple to keep on replacing our parts indefinitely as they wear out and break down, the way yours have always been replaced. You've even had an entire body replaced."

"But surely it would be theoretically possible for you to be transferred into-"

"No. It isn't. Not even in theory. We don't have positronic brains and ours aren't transferable, so we can't simply ask someone to scoop us out of a body that we're finished with and put us into a nice shiny new one. You can't comprehend the fact that humans inevitably have to reach a point where they're incapable of being repaired any more. But that's all right. Why should anyone expect you to be able to conceive the inconceivable? I'm going to die soon and that's all there is to it. And I want to reassure you at least in one respect, Andrew: you'll be well provided for financially when I go."

"But I am already quite well provi-"

"Yes. I know that. All the same, things can change very quickly, sometimes. We think we live in a very secure world, but other civilizations have felt just as smug and they had reason sooner or later to see that they were wrong. Anyway, Andrew: I'm the last of the Charneys. I have no heirs except you. There are collateral relatives descended from my great-aunt, but they don't count. I don't know them and I don't care about them. I care about you. The money I control personally will be left in trust in your name and you'll continue to be economically secure as far into the future as anyone can foresee."

"This is unnecessary, Paul," Andrew said, with difficulty. He had to admit to himself that what Paul had said about his not understanding death, not being able to understand it, was true. In all this time he had not really managed to get used to the deaths of the Charneys.

Paul said, "Let's not argue, all right? I can't take the money with me and there isn't anything I'd rather do with it than leave it to you, so that's the way it's going to be. And I don't want to consume any more of my remaining life-span discussing the matter with you. Let's talk about something else. -What are you working on these days?"

"Biology, still."

"What aspect in particular?"

"Metabolism."

"Robot metabolism, you mean? There isn't any such thing, is there? Or is there? Do you mean android metabolism? Human metabolism?"

"All three," Andrew said. " A synthesis of sorts." He paused, and then he went plunging ahead. Why hold anything back from Paul? "I've been designing a system that would allow androids-I mean myself; I am still the only functioning android, am I not?-to draw energy from the combustion of hydrocarbons rather than from atomic cells."

Paul gave him a long, slow look.

"You mean," he said finally, "that you want to make it possible for an android to be able to breathe and eat the same way humans do?"

"Yes."

"You've never mentioned any such project as this to me before, Andrew. Is it something new?"

"Not really. In truth, Paul, it is the reason I began all this biological research in the first place."

Paul nodded abstractedly. It was as though he was listening from a very great distance. He seemed to be having a difficult time absorbing what Andrew was telling him.

"And have you achieved anything significant so far?" he asked, after a time.

"I am approaching something significant," Andrew said. "It needs more work but I think I have succeeded in designing a compact combustion chamber that will be adequate for catalyzed controlled breakdown."

"But why, Andrew? What's the point of it? You know that it can't possibly be as efficient as the atomic cell your body uses now."

"Very likely not," said Andrew. "But it ought to be efficient enough. At least as efficient as the system that the human body uses, I would say, and not all that different from it in fundamental principle. The main problem with the atomic cell, Paul, is that it is inhuman. My energy-my very life, you could say-is drawn from a source that is wholly other than human. And I am not content with that."