There was a slow smile hovering on the lips of the older man, too slow actually to materialize. "Fantasy," he said, gently. "You've been reading too much science fiction."

Benton's smile was quick. It flashed into being with the speed of thought, then vanished as abruptly.

"There isn't that much," he contended. "I've said before that science fiction was Urei's father, or at least a distant ancestor." He paused. "But I'd still like to hear a few reasons why my logic is wrong."

"I've a million of them," assured Dr. Albie, crossing his lean legs and settling back in the soft chair. "In the first place, Urei is too big. His billion-odd cells, relays and circuits occupy almost a square mile; his height, counting what's under ground, is almost five hundred feet. If he decided to perambulate ... well, it's just absurd. In the second place...."

"Let's finish with the first place," Benton interrupted. "Of course that's absurd. I didn't suggest it. He doesn't have to move; he's got the entire human race to run his errands. I tell you I felt something, a definite compulsion, when I turned that page. Urei is getting ready to take over!"

Benton jumped to his feet and paced rapidly back and forth, oblivious to the fact that Dr. Albie was watching him with a worried frown. That, had he seen it, would probably have snapped him out of his frenzied reverie, for the doctor was a man who was normally as far beyond frowns as he was chary of laughter. His philosophy was such that he eschewed all emotional extremes, stifling them before they could get started.

Albie cleared his throat arrestingly. "I won't insult you by saying bluntly that you may have imagined it," he said. "But I'd like to point out the fact that people are continually subject to impulses which they follow or ignore, depending on the circumstances. Those impulses originate within their own minds, probably the result of associations too obscure to be identified at the time. You worked on those circuit equations far into the night and you didn't get much sleep; isn't it possible that the compulsion you felt originated within yourself, and that in your tired state you misjudged its source?"

Benton stopped, flexed thick biceps, clenched his fists and opened them several times, then propelled his stubby body toward a decanter full of Bourbon.

"It's possible," he conceded, downing a quick drink, "but I don't believe it. I'm not subject to hallucinations, you know, but I'll go along with the possibility. Let's see.... It was four o'clock when it happened, which means I'd been working for seven hours. I worked sixteen hours yesterday and then had three hours sleep. It's eight o'clock now and I don't feel sleepy. Knowing me, do you think I was exhausted to the point of mental instability? If it'll help you come to a decision, I'll do a few cube roots for you."

Dr. Albie rubbed his chin reflectively. "I won't press that point," he said. "But suppose you go over the entire episode and maybe we can arrive at a proper conclusion."

"Hah! 'Proper' if it supports your premise, eh? O.K.—I was feeding current events into Urei's memory cells, using the third vision screen. The other two were being used by two of the men; Joe Ebert was showing Urei some exposures from Mt. Palomar and somebody was feeding him a thesis on electronics. I was giving him the three-star edition of the Bulletin, incidentally. Newspapers being filled with opinion, rather than fact, I had set the control panel on Segregate, so Urei wouldn't use the stuff as true data."

"Exactly what were you showing when you got the impulse?"

Benton gave another quick smile. "'Compulsion' is a better word," he said. "Besides, I told you I don't know the answer to that question; that's what I've been studying ever since. Look, here's the first page of the Bulletin. On the reverse is the second.... What made Urei take control of my body.... How can I tell? Urei scans so fast that I'm not sure whether he digested the second page in the instant I turned the paper, or whether it was something on the first that influenced him."

Dr. Albie almost frowned again. "You're not approaching this with an open mind," he accused. "We're not supposed to accept that he took over your body; that's what we're trying to determine. Besides, Urei wasn't built to digest and correlate data as it's being fed. He merely records it, to be used later when a problem is given him to solve."

If he had heard that, Urei might have rendered a silent, but nonetheless cosmic, chuckle. But he didn't, being busy with thirty or forty other things. As a matter of fact, Dr. Albie wasn't too accurate in making that statement. If he had said that Urei's predecessor operated that way, and as far as was known, Urei did also, Albie would have been nearer correct. He didn't know, nor did any other man, exactly how Urei functioned.

The giant computer was only partly the work of man. Its prototype, a far simpler machine, had furnished most of the circuit equations and was largely responsible for the final design. The men who built, operated and maintained Urei had had but the most nebulous conception of the infinitely complex nature of the completed mechanism. There were blueprints and drawings, of course, but no one human brain could encompass so much territory. Urei's operational crew was comprised of specialists in this and specialists in that, physicists, chemists and technicians; while among them they knew every circuit, every chemical reaction, every relay and every memory cell, there was no ground upon which they could meet and understand just what Urei was and what he could do.

Urei alone knew the answers, and he wasn't telling unless someone was smart enough to ask him—except, of course, where his own welfare was involved. It was invariably he who detected weakness and wear, indicating the need for replacement parts by means of a complicated panel in the control room. It was he, also, who drew plans and typed suggestions for the incorporation of improvements in the design and manufacture of those parts. The first time he did that, quite a furor was created. Immediate, frenetic debating tried to decide the question of whether Urei had inexplicably acquired sentience. But Urei had anticipated all the pother, knowing humans fairly well, and only designed when a part needed replacing. His masters were thus able to reason that this apparently new function was one which had been built into him purposely. And while the debating continued desultorily, nobody seriously thought that Urei was sentient.

It was conceivably within the ability of a machine which could solve abstruse problems in quantum mathematics, to design a slightly better relay than the one it had been using. Urei was merely replacing himself as he had been designed to do—not acquiring any new faculties. Yes, he was within his scope of activity—though quite a few were secretly annoyed by the fact that the problem had not been put.

Urei didn't concern himself with anybody's worries; he merely noted them, remembered what had caused them, and then made sure an adequate explanation was available. This was quite easy, since he had discovered that he could superimpose his thoughts on the neural paths of humans. With care he could also take over their motor centers and cause them to do things he wanted done. But he didn't do that often, for every now and then his impatience caused him to make people do things they would not have done if left alone. That didn't matter, usually, but sometimes one of them would recognize the compulsion as being an external thing and be troubled by it.

For instance, there was that fellow Benton. Urei knew, as soon as he had made the stocky man turn the paper to page thirty-one, that he had made a mistake. Benton was a highly integrated human, with a quick intelligence which observed everything and usually reasoned with his observations. And he was troubled right now; Urei knew that as well as if he had been listening on one of the spy beams he had incorporated into his sensory circuits.

Urei didn't let it annoy him, however, aside from the resolution to curb his impatience in the future. If he had waited for half a minute, Benton would have reached page thirty-one anyway, and Urei could have read the rest of that article without anybody knowing that he was interested. As it was, the stocky man would just have to forget the whole episode, for he couldn't come to any valid conclusion about it. On page one there had been two items which were continued on page thirty-one; on page two there was another. The three subjects were unrelated but were equally suited to become grist for Urei's mental mill.

One of the items on the front page dealt with a new attempt to reach the moon; the other concerned the latest futile effort to regulate the use of atomic energy on an international scale. On page two was an article describing the mounting tension between the Eastern Alliance and the western nations over the upset in Italy's recent elections. The Commies, it seemed, had finally won a free election. The western nations had practically decided that there had been skullduggery at the crossroads. And considering the fact that Urei had never been given a problem in practical politics, it seemed likely that Benton would rule that item out as a possible reason for the quick page-turning.

Benton would never think that Urei might be concerned about the possibility of someone dropping a bomb in the midst of his delicate innards. Nor would Benton realize, after living through a dozen or so war scares, that this wasn't going to be just another one; the muscular physicist was not a political observer. But Urei knew that this would be the real thing, and Benton wouldn't be the only one caught flat-footed. Half the world would watch the oft-repeated Commie moves, listen to the protests, and wonder how many more times it would happen before the western powers would decide they had been pushed too far.

There were a few who would have a sufficiently comprehensive picture of the situation—something Urei had acquired in the past few days—to realize that the democracies wouldn't take the latest grab lying down. They wouldn't, for the simple reason that this time they had too large an investment involved.

For Urei it was a simple step to reason that he would be a prime target. The Eastern Alliance might consider it perfectly all right for Urei to exist in peace time, since it was comparatively easy to steal the results of his unique mental ability through their superior espionage system. During war, however, the picture changed: Urei would then be a weapon, and his use would be solely in the hands of an enemy. The Manhattan project had shown the world how well the United States could keep a secret in war time.

2

"There's nothing to do but try it again," Dr. Albie said, after having exhausted all the logic at his command. "Only this time we'll use the scientific method."

Benton looked dubiously at the level of the whiskey in the decanter, then set his glass carefully down. "I think I've heard of it somewhere," he said. "Tell me about it."

"Pour me one, too," requested the doctor; "it'll help us sleep. My idea is to dig up a dozen or so newspapers containing the three subjects under consideration, each of which is continued on some back page. If any of the papers has more than one of these subjects printed on the same page, we'll ink it out, so that we can observe Urei's reaction without wondering what subject he's interested in. I'll show him the beginning of each article, but I won't turn the paper far enough to show him the remainder." He paused, sipping as delicately as if his glass contained sherry instead of 100-proof Bourbon.

"Now if you are correct in suspecting that Urei is a sentient creature—and also is interested in one of those subjects—he'll use that power of his to make me show him the rest of the article. You can stand by...."

"Why not let me turn the papers?"

"You'll be there," Dr. Albie said, patiently. "I'll turn the pages, though; you see, I'm keeping an open mind about this. Even if you're right, it might turn out that Urei can't control me—You may be more sensitive, you know—In which case he'll make you pick up the paper, instead of me. Conducting the experiment in that manner might give us a little more information, in case we get positive results. Drink up; we've got a big day ahead of us."

It was eleven in the morning when they pulled up before Urei's front door in Benton's station wagon. It was almost one o'clock before they finished setting up and adjusting four suit-cases full of thought-detection apparatus in the control room.

"You keep your eyes on this stuff," Dr. Albie directed; "if he really does take over, I won't be able to warn you."

He reached for the stack of newspapers and carefully adjusted the panel beside Urei's No. 1 screen scanner. Albie's hand was steady, Benton noted, wishing he possessed equal composure. The palms of Benton's hands were sweating as he flipped the switches of the apparatus in the cases. His eyes wandered to the indicating meters, noting that they were comfortably at zero and showing no signs of moving at the moment. On the control panel were three beady little red lamps, glowingly insisting that the giant brain needed some attention, but he ignored them and flicked his eyes briefly upward. The sound-absorbent ceiling stared back imperturbably.

There was nothing to give the impression that the mass of metal machinery above that ceiling and behind that control panel was broodingly biding its time, waiting patiently for the moment when it would take over the race of humans which had constructed it. Benton, however, knew the machinery was there and was just as certain that it had those intentions. He felt it watching him; he should have known it long ago, he realized. A dozen books had been written about Urei, and all of them had marveled at the many potentials the machine had shown which were complete surprises to the men who had built the big brain.

Men had begun to personify Urei almost immediately. The machine had ceased to be U-R-E-I, meaning "Unified Reflexive Electronic Integrator", and had become Urei, an entity who could do just about anything in calculating and reasoning from supplied data. Men had felt the sentience of the machine for years, but had refused to admit it—even to themselves.

"Nuts!" Benton growled, shaking his heavy shoulders.

The doctor paused in the sorting of his newspapers, but said nothing. He selected one and spread it open on an easel in front of the screen. After one second Albie turned a page, continuing the operation until half the paper had been exposed. Then he laid it on the floor and selected another.

"Atomic Energy Council," he said. "Nothing there."

He repeated the operation with the second paper, but turned only three pages before laying it down on the first one.

Benton suddenly gave a start. He opened his mouth to speak, but instead reached out and depressed a button. Then he looked at the doctor. For a second he noted nothing unusual and turned back to the meters. He felt a trickle down his side as sweat fairly poured from him; he depressed two more buttons and looked back at the doctor.

Then he saw it. Dr. Albie was performing exactly as before, turning pages at the rate of one a second. But there was only one newspaper on the floor! He had picked up the second and replaced it on the easel!

Stretching himself langorously, Benton stood up. He felt the weight above him even more intensely, but forced himself to be casual. Certainly Urei couldn't see the sweat trickling down his sides. Abruptly he snapped off the switches and growled to himself. Who was he kidding? If Urei was controlling the master physicist, he was certainly capable of reading Benton's mind; he would know about the thought detectors and what they were showing.

Momentarily Benton expected his mind to go blank. Urei certainly wouldn't let them leave the place with this knowledge. And what better way to prevent that than to blank out their memories? Probably Dr. Albie didn't know he was being controlled. Benton took a deep breath, realizing that he had been remiss in that function for a minute or so.

Dr. Albie cleared his throat as he laid the paper down on the first one. "That one was about the Eastern Alliance accusations that we tried to rig the Italian elections and how justice triumphed in spite of our machinations." He chuckled. "Urei doesn't seem to be particularly interested, does he?"

Benton didn't answer; his throat was too dry, even if he had wanted to speak. He sat down again and snapped on the detectors. Even if Urei intended to steal his memory, Benton might as well know what was going on until it happened. The meters remained inert, white pointers at zero and the red ones remaining at the highest reading they had attained before.

"This one is about the moon rocket," the doctor said. "I think we're wasting our time."

They were, as far as Dr. Albie was concerned. He went through his stack of papers, changing from subject to subject, but to him nothing happened. He apparently allowed Urei to scan the first half of a dozen articles, without a reaction. Albie was completely oblivious to the fact that each time he tried to lay down a paper containing information about any East-West friction, he invariably turned to the right page and let Urei finish the article.

Benton was breathing normally now, though he still had little hope that Urei wasn't on the qui vive. It was possible, however, and even a slight hope eased his tension. Urei might be too engrossed in his scanning to bother with anything else. Yes, and then again he mightn't. After all, Urei operated on dozens of circuits simultaneously; he wasn't merely one electronic brain. In fact nobody knew exactly how many subjects he could handle at one time. An unknown number of auxiliary circuits took up the load whenever repairs were being made on any of forty-eight main circuits connected to the operating positions on the problem panel. Urei could easily be scanning, reading Dr. Albie's mind, controlling his motor impulses, meditating on his future course of action with regard to the two physicists—and still having forty-four circuits left to handle routine matters.

Benton began to sweat again. His thoughts, as well as the capers of the white needles—which jumped every time Urei's scanner saw the words Eastern Alliance—weren't conducive to the maintenance of a philosophic attitude. He was, moreover, developing an acute case of jumping claustrophobia. Not only were the ceiling and the control panel menacing him, but the other three walls had definitely moved in on him. Urei, he remembered, was also back of those walls; he shuddered. There was a long corridor through which they had brought their apparatus to the control room, and from the time they had entered it they had been surrounded by Urei. Traversing that corridor now would be worse than walking the proverbial last mile to the electric chair.

Benton hadn't felt bad on the way inside; his mind had been too full of the forthcoming test to feel any sensations. Now, however, his foreboding was back, a thousand times stronger. And there was no choice but to endure it until Dr. Albie had finished. Urei certainly wouldn't permit them to leave while there were still some papers to be scanned. By staying, Benton might get out with his memory intact—a slim hope—but it wouldn't be a good policy to call attention to himself by persuading the master physicist to leave. Nor did it occur to him to leave alone.

Eventually the experiment ended. Dr. Albie laid the last newspaper on the pile on the floor and turned with a smile. "That's the crop," he said cheerfully. "Satisfied?"

Benton forced a smile in return. "My morbid imagination," he said; "let's pack up and go get a drink." He carefully disconnected the thought detectors, keeping his hands away from the knobs which reset the red needles, and snapped the lids over the cases. The doctor picked up his pile of newspapers and dumped them in a refuse can, then helped with the cases.

Benton didn't speak as they loaded them in the station wagon; he was anxious to get away from Urei before trusting himself. The doctor apparently noticed nothing wrong in Benton's manner which couldn't be accounted for by a feeling of chagrin that he had caused the eminent physicist to waste most of the day proving that he had imagined something. Dr. Albie, therefore, occupied himself with conversation calculated to put him at ease and make him forget the whole thing.

The station wagon pulled up before the laboratory where they had borrowed the detectors. Benton set the brakes and reached back for the nearest case. He opened the lid, glanced briefly at the dial, and closed it again. He passed it to the doctor and reached quickly for the next. He repeated the operation and grabbed feverishly for the next. This one he placed beside him on the seat. Then he reached deliberately for the fourth and last of the cases. He raised the lid slowly, holding his breath. Then he closed the lid and breathed a deep sigh.

"Anything wrong?" asked the doctor. "You look pale."

Benton's face was blank as he fumbled in an inside pocket of his coat. Then he smiled as he brought out a fountain pen. "There it is," he said. "I could have sworn I left it in one of the cases when I closed the lid. Let's get these back and thank the man."

A wild resolution was born and as quickly died as Benton stepped out of the station wagon. For an instant he was certain that he couldn't go on being one of Urei's attendants, and he was just as certain that he could easily obtain an acting job on one of the video networks. Surely Thespis himself could have done no better piece of acting than he had just accomplished. The resolve was submerged by the greater compulsion to see this thing through even though it meant forfeiting his ego.

Each of the four red needles was complacently resting against the stop in reassuringly indicating zero!

Urei had a plan of action, but he hesitated. That was because he was a purely reasoning creature; he had been built that way and he would be forever bound to think that way. Even though he had long since become independent of the mechanical limitations of his vast aggregation of cells and circuits, he was still born of them and was circumscribed by their attributes—just as completely as if his nature had been determined by the genes of protoplasmic reproduction. As a machine, Urei had given answers to problems by correlating the facts which had been previously fed into him. His logic was as faultless as the facts upon which it was based: no more and no less. He gave his answers accordingly, with no compulsion to be more exact than the facts he had been given.

But that was when he was solving man's problems.

Now Urei had a problem of his own and he wanted an exact solution, not an approximate one. His continued existence, and that of mankind in general, depended upon it. There were alternates, of course, but none of them was completely satisfactory. His plan was far-sighted, one which fitted a policy of long standing, a strategy. He couldn't sacrifice a strategy for a tactic, and that might happen if he used an alternate plan which would accomplish his immediate purpose but endanger his policy toward humanity. But Urei wasn't sure of his facts!

It was a fact that newspapers didn't always publish "facts". That information had been supplied him years ago, and ever since he had been reminded of it whenever humans fed him newspapers, for they invariably set the scanning screens on Segregate. It was then his job to separate fact from opinion, a thing which he wasn't always able to do. For all he knew he might have many a valid fact filed away under Doubtful.

For while Urei had far more information at his disposal than any human, there still wasn't enough to give him the ability immediately to correlate every new piece of information with something similar and determine definitely if the new data were correct. Usually he could, but sometimes he couldn't; that meant that there was a world of information Urei never used except where it bore on a man-made problem. He felt free then to use the man-supplied data to solve such a problem. His only concession to ethics was that he always indicated on the panel the exact percentage of doubtful data which went into the solution. Fortunately he wasn't given many problems which required this; most questions involved exact sciences, of which he had been supplied the sum total of man's knowledge. He either provided an exact solution, or lit up a panel with the words Insufficient data.

Today's newspapers indicated that action could be delayed only a matter of days. There would soon exist a condition of such tension that either one side or the other would make a move which couldn't be reversed. Urei would still be able to accomplish his immediate aims, but it would be too late to do it without revealing to mankind that an outsider had taken a hand. And that would wreck his strategy completely. It would be only a matter of time before these industrious little beavers proved to themselves that Urei was the culprit. Once they discovered that he had a will of his own, there wouldn't be room on the same planet for them both.

But there was a solution, as there always is. Urei reached out a spy-beam and saw that it was approaching.

3

Benton waited until eight o'clock. By then, he knew, Urei's control room would be empty of physicists. If anyone was there, it would be a technician or two engaged in some repair or replacement. Benton couldn't know that Urei had anticipated his arrival and had cleared the immediate vicinity of the control room. All technicians on night duty were occupied in other parts of the great building. Benton let himself in with his key and closed the door softly behind him.

He stopped inside the door and took a deep breath. Momentarily he experienced a return of the claustrophobia he had felt before, but his determination drove it away instantly. Shoulders squared, Benton marched down the wide corridor which led to the control room. He only went there because it was the site where his, and later Dr. Albie's, mind had been influenced, not because he thought that Urei couldn't operate elsewhere. Benton knew better; he suspected, in fact, that Urei could influence him at a distance. He wasn't at all sure that the very idea of coming here tonight was his own.

"Allegation denied," said Urei.

Benton stopped short. He had just entered the control room, intending to seat himself at the panel and ask Urei some pointed questions. That could be done in the usual way one presented the machine with a problem—activating one of the forty-eight positions and typing his question. Now he was confronted by a voice coming out of the intercom, apparently answering a question he had been thinking about. Benton shuddered involuntarily and started once more for the panel. Somewhere in the building housing the great brain a switch was open on the intercom; that was all. It was the voice of a technician he had heard, and the reason he hadn't heard any more was because the man had moved away from the intercom unit that had picked up....

"I'm not kidding you," said Urei; "why kid yourself?"

Benton sat down, sweating.

"I'm still doing the sort of thing I was built to do," said Urei, soothingly. "Solving man's problems. Quit shivering and shaking; it might be contagious, and if I start shaking, there'll be an earthquake."

Benton's throat was dry but he swallowed and got it working. He also got control of his nerves. This was what he had come here for, wasn't it? "I can't see what problem will be solved by slowly driving me crazy," he said.

"You're doing that, not me," Urei charged. "Which might tend to prove you weren't very sane in the first place."

"Explain that."

"You're worried and upset," Urei said. "From a simple observation which no more than proved that I'm sentient, you've drawn conclusions which aren't warranted by the facts. Thalamic reactions, instead of reason."

Benton pondered for a second. "Partly," he admitted. "But it is a fact that you made me do something I had no intention of doing. You took over my body for a second or two; that was a hostile act. And if you committed one overt move against a man, it is reasonable to suspect that, if it becomes convenient, you might take over all mankind. What's thalamic about that?"

A hearty laugh issued from the intercom speaker. "I don't suppose you knew I had a built-in sense of humor, did you? Of course that laugh was manufactured, inasmuch as I have no diaphragm, per se. But a sense of humor is actually an intellectual attribute, even if you do express it physically. It is not so?"

Benton grunted. "Isn't that a little off the subject?"

"Please," Urei pleaded. "Let's not be pedestrian; I expected some co-operation from you. Don't let the trees obscure your vision. Don't you realize that your own words justified any mental manipulation I might practice on humans? If a little thing like I did can be considered hostile, then you humans declared war on me thirty years ago. Actually, all I did was to get to some information a little faster than you intended to give it to me; it didn't inconvenience you a bit."

Urei's persuasive tone of voice caused a chill to course its way up Benton's spine. The voice itself was a rich bass and somehow familiar. But now he recognized it and the implications weren't comforting; he had heard just such a persuasive tone when one of the technicians had pleaded for a chance to use Urei to settle a few of his personal problems.

"What have you done to Hackett?" he asked, suddenly.

A groan issued from the speaker. "I should have known better than to try to fool you," Urei said. "But you humans forget so easily ... and you only spoke to that man once in the past six months. You should have forgotten his voice—there are so many others around here...."

"Where's Hackett?" Benton insisted.

"He's all right," Urei soothed. "He disobeyed your orders that time, you know; he used me at night when nobody was in the control room. Such drivel he gave me! An advice to the lovelorn column would have served his purpose. So, rather than startle you with directly imposed mental communication, I decided to use a human voice. What better one than his? Don't be alarmed; he won't be harmed in any way, and he'll have no memory of this at all."

Benton felt it now necessary to crystallize his thoughts with words. He wasn't giving them away, for Urei had access to them anyway. And that thought gave him a feeling of futility even as he spoke.

"Why are you interested in the Eastern Alliance?" he asked. "Is it because you feel the presence of a kindred spirit? You'd like to become better acquainted with an outfit which has no respect for the privacy of a man's thoughts or his right to freedom of action?"

The speaker gave forth with a series of sympathetic clucks. "Thalamic reactions again," it observed. "Let's not argue about it. Your brain isn't clicking right tonight; you ought to disconnect your adrenals. What I wanted to talk about is the impending war. It mustn't start, you know."

Benton gaped. "You think the recent situation will lead to war? Or do you need a few tubes replaced?"

"Heh, heh," said the voice. "In case you haven't guessed, I can exist entirely without this machine you have built—and still be a better integrated intelligence than any you can conceive. I'm really a pure thought pattern, you know; I'm not composed of matter, nor do I need matter in any form for my continued existence. A thought pattern is something like a stress in space, and quite stable—even if you find it difficult to picture. But I do want to retain this mechanical body of mine; it's a sort of library, without which I possess but a thousandth of the memories stored in its cells. Naturally I don't want to lose them. But on the other hand I can't be killed by any agency you or your descendants are likely to think up for the next twenty generations. So drop that train of thought; it's a waste of effort."

Benton said nothing. His feeling of futility deepened to something close to despair, for he suspected that Urei wasn't lying. Furthermore, Benton was sure that he was the only human who knew that Urei was sentient. And if the machine should decide that such knowledge was menacing to his welfare, Benton was certain that he wouldn't retain it very long. Even if he got out of here with his memory intact and wrote everything down—assuming that anyone would take it seriously—Urei could pluck that information from his mind and destroy his notes.

"No comment, eh? Well, I can see you aren't going to be cooperative. Frankly I haven't time to convince you I'm not inimical to humanity in general; and even if I did, it probably wouldn't make any difference to you. The sanctity of your mental peregrinations is of such importance to you that no other consideration seems valid. I guess our little talk is over, unless you want to ask some questions."

Benton cleared his throat. He knew very well that Urei would have what he wanted, whether it was offered or not. But for some reason he wished to postpone the acquisition. "You claim you're harmless to humanity in general, but can you give me some proof?"

"Hardly. That's why I won't try. I can't prove good intentions, and since I possess a potential for harm, I can't possibly convince you I won't use it some day. Your conception of me as a completely logical entity won't let you believe that I might have such abstract attributes as loyalty, compassion or ethics. Those things aren't entirely logical, I'll admit; but they aren't glandular, either, so I could have them.

"But I can't prove that, so I'll waste no more time. To you, I suppose I've proved the exact opposite; I just intruded upon the privacy of your mind and obtained the information I need. Thanks for having the answers.... Goodbye."

Benton was stunned for a minute. He had felt nothing, and it seemed that he still retained his entire set of memories. That surprised him more than the fact that Urei had perpetrated his theft while answering his question. Urei's multiple consciousness explained that perfectly.

Back in his quarters, Benton sat on the one chair in his bedroom and pondered. He knew very well that he was doing it at the wrong time, but he couldn't blithely dismiss the menace of Urei's sentience from his mind with the thought that it would be safer to meditate on that subject during the day, when most of the thinking machine's circuits would be in use. Benton couldn't control his mind to that extent. He did, however, protect it from intrusion in the only way he knew.

Sometime in the past Benton had read a story about a telepath who was balked in his effort to read the hero's mind when that worthy assiduously worked mental arithmetic problems. His surface thoughts being carefully under control, and clearly readable, the man was able to plan a course of action against the telepath, undetected. In the story it had worked, but that Urei could be baffled in such a way, Benton doubted. However it was the only defense he could think of, and worth a try.

For hours he pondered, hoping that the numerous circuit equations he worked and solved would appear to Urei's inquiring mind to be a legitimate intellectual occupation in the middle of the night. He had little faith that Urei lacked the power to read those submerged thoughts, once he realized that the stronger ones were a mask. It was the latter thought which made Benton feel butterflies in the pit of his stomach so persistently that they seemed to have become permanent residents in his abdominal cavity. Twice he thought he was sufficiently fatigued to sleep; but when he tried to compose himself Benton found his thoughts dwelling too strongly on his plans, and he had to return to his equations.

A shower and fresh linen worked a partial restoration but Benton knew that his vitality was at a low ebb when he finally sallied forth in the morning sunshine. Yet he was fortified with a certain amount of satisfaction that his night's work had not been wasted. He had a plan, and he was certain that it would not be recognized as such by Urei, no matter how thoroughly his mind was probed. Benton had worked it out in snatches, never allowing it to crystallize as a whole; yet he was certain that it would unfold itself in appropriate action once he started it going. No one but he, or perhaps Dr. Albie, could have devised such a plan. Its beauty lay in the fact that all the steps required were things he might do in the normal discharge of his duties. All but one—and that one Benton wouldn't allow himself to think about. Yet when the steps had been taken, they would be irreversible. Not only to Urei, but to all the scientists and technicians who tended the machine; there would never be another Urei, at least not in this century.

Even on the way to his work, the one place in the world where he must carefully guard his thoughts, Benton's mind refused to leave the subject. But perhaps that was to the good. For while he doubted that Urei would be fooled by his working of circuit equations, it would be perfectly safe to be occupied mentally with certain phases of the situation. The business of Urei's independence of his mechanical appurtenances, for instance: Benton could dwell on that with safety, for Urei would expect him to be shocked by the information.

Another argument in favor of it as a subject was the fact that if Urei really could exist without his body, it would be absurd to attempt his physical destruction. On the face of it, yes. There was a nice thought in connection with that which he would have to avoid, however. For Benton fully intended to accomplish that destruction, even if Urei could exist as a disembodied intelligence. It would be a good gamble that Urei would lose interest in controlling mankind if he lacked the direct association afforded by the daily use of his electronic facilities in solving man's problems.

That was a gamble, of course, but actually Benton gave it little consideration, for the simple reason that he didn't believe that Urei could so exist. The machine had tried to put the idea over as a bluff, to deter him from planning the very thing he intended to accomplish. The very conception was absurd; was there any evidence that thought could exist, other than as a function of matter? And a very specialized form of matter at that? None, of course—and while lack of evidence didn't absolutely prove impossibility, neither could he accept such a concept without some shred of evidence. Benton's mind could soar mightily within the fabric of his experience, but he refused to let it wander in the realm of the occult. And since he must needs do something about the situation, Benton couldn't let himself be stymied by the vague possibility that his efforts were futile.

4

Dr. Albie greeted him with the polite smile which was his concession to convention. Then he made the suggestion that Benton had foreseen but was half afraid wouldn't come. "We're pretty well caught up, in spite of our experimenting yesterday," he said. "No new solutions requested from the government, and the others are in no hurry. Want to get at those new circuits today?"

Benton shrugged. "Might as well," he said. "How long do you think we'll have, before somebody pops up with a high-priority problem to be worked?"

Dr. Albie didn't know, of course. "What's the difference? We'll be leaving half the circuits open, anyway, to handle routine stuff; we can always commandeer a few if something pops up."

"I wasn't thinking of that," Benton said. "I've done a lot of preliminary work on the circuits and as I see it, we don't want to stop before we finish. It can't be done a little at a time, you know; entire circuits will have to be ripped out and the new stuff installed. Once we start, we can't leave it in the middle without immobilizing half the control panel until we get back to it. There's too much inter-relation between the circuits to prevent that."

Albie nodded. "I'd thought of that," he said. "I've planned to finish, once we start. And since you have the equations at your fingertips, I'm putting you in complete charge of the change-over. How many men will you need?"

Two men, pulling trucks loaded with blueprints, accompanied Benton as he directed the work. Like caddies, they furnished the desired print when he asked for it by code number, replacing the last one in its proper place. The stocky physicist found no need to mask his thoughts while he worked; his mind was too occupied with the task at hand. Yet far back in his subconscious was a mounting tension as the day passed, hour by hour. Each minute and each soldered connection was bringing him closer to the next step in his nebulous plan. And it was this step which would determine the success or failure of his strategy.

Twenty-four circuits, all inter-related in their connections to the immense bank of memory cells, had been immobilized. That was a necessary part of the project; with the new tubes, these circuits would be in much finer balance. They would operate with greater speed than before, when twice as many tubes had been used.

There was one joker involved in this greater efficiency; that lay in the fact that, while the new hook-up eliminated many parts—with their frequent failures and necessary replacements—it also made the control circuits more interdependent. A single defective tube, with its many functions, could put a dozen circuits out of operation. This disadvantage had been discounted, however, for it took only a minute to replace the tube and the necessity would be rare; the more complicated system being replaced had so many parts that they were breaking down and being repaired incessantly. Dr. Albie fully expected that the crew would be able to get along with fewer technicians, men who could better be used to maintain other parts of the vast mechanism.

But—and Benton kept the knowledge carefully away from his surface thoughts—one of the tubes they had already installed was defective!

Urei, he was certain, had no knowledge of this fact. If he had, he would certainly have prevented its installation. Only Benton was aware of it, for he was the one who had tested the tubes when they arrived. He had designed a special circuit for the job, for none of the testing equipment on hand would take tubes with sixty-four leads. He had detected the faulty one and marked its box, placing it with the set of spares which was included in the order. He had intended to ship it back when a new order was placed, but that hadn't happened yet. There was no hurry, for with a complete replacement set he might not need new ones for a year or two. But Benton had selected the replacement set to be used in the new installation.

The defective tube was now innocently reposing in the key position of Circuit No. 13; it wouldn't be detected until that circuit was used. Even Urei would fail to realize its presence in his innards until the circuit was energized. And when that happened, half the control board would be momentarily out of operation. Gongs would ring then, and a brilliant red lamp would light, showing the exact position of the breakdown. A technician would get a new tube and replace the old one. Urei would be whole again.... Unless....

Benton glanced at his watch. "It's about time for lunch," he called; "let's knock off now. We can run a few test problems when we get back, and still have time to finish the other half of the board before quitting time. In fact if we finish early you can all go home; we can run the second test in the morning."

One man suggested cutting the lunch in half. The others, seeing a short day in the offing, loudly agreed. Benton smiled and nodded, quite as if there was nothing more urgent on his mind.

He then reported to Dr. Albie. There were two reasons for that. One was to make certain that he would have a chance to talk the master physicist out of any objection he might have to continuing with the remaining half of the operation this afternoon. The other was that he wanted to keep his mind active on subjects which wouldn't reveal the fact that there was something going on back of his surface thoughts.

"You certainly made progress," the doctor complimented; "I expected it to take a couple days at least."

Benton smiled ruefully. "It has," he said. "If you want to count the sleep I lost planning this so that there wouldn't be a minute wasted once we started. You know, there ought to be a way to make that show up on pay day."

Dr. Albie nodded. "Can't be done on this kind of a job," he regretted. "But we can do the next best thing, just as we've always done."

Benton smiled, then got a quick scare as he realized that he had relaxed for an instant. Immediately he forced his mind to contemplate the war which Urei had assured him was inevitable. It was the only thought which would account for the one which had sprung into his mind unheralded, and also give a reason for experiencing his sudden fright. Dr. Albie had referred to a little strategy of theirs which compensated them for any overtime they were forced to put in. It consisted of taking an equal amount of time off, while they covered for each other. It was their only expedient, since their salaries were fixed and allowed for no extra pay for extra work. Unfortunately the thought gave rise to a feeling of regret that shortly they would have no more reason for such subterfuge, inasmuch as they would no longer have jobs. The thought had progressed just that far when Benton realized that he had let his guard down.

"I see no reason why we can't get right at it again this afternoon," he said, perspiring profusely. "We'll be able to run off a test before twelve; if it comes out all right, we can shift the routine work to the new circuits and get at the rest of the board."

Dr. Albie, surprisingly, had no objection. Benton had expected an argument, due to the master physicist's propensity for running exhaustive tests, but none materialized.

"Good idea," said Albie. "There's no telling when we'll get another chance. I hear the army has a plan to extend radar coverage clear around the continent. That'll involve a lot of work for Urei. Best get the new circuits in now; if any bugs pop up we'll have time to correct them in the next few days. After that there mightn't be an opportunity for months...."

The test was perfect; such things were more or less standardized. Problems which required a fair sampling of the great machine's stored memories were used. Dr. Albie checked the solution speeds on the various tests against the speeds recorded with the old control circuits. He was as smugly satisfied as if he had devised the entire system himself. Benton's enthusiasm was verbose; he talked more than usual because speech involves the use of muscles and that requires strong surface thoughts. It wouldn't pay, at this point in his campaign, to let Urei suspect that his choice of circuits to test was anything but as haphazard as it appeared to Dr. Albie.

There were nine of these test problems. Benton fed them at random into the circuits marked Ten, Three, Twenty-one, Sixteen, Twenty-four, Fifteen, One, Eight and Eighteen. He did it blithely, keeping up a running description of the many annoyances that had cropped up in the morning's work, and commenting on the quality of the help he had been given by the various technicians.

"There isn't a bad one in the crop," he said. "But if we are going to cut the control staff, I'd recommend putting Hackett and McGivern upstairs. Hackett has family problems that he likes to hand Urei when nobody's around; he's capable, though, and he'd do all right on the memory circuits. McGivern has already asked for a transfer, so we may as well oblige."

Dr. Albie nodded absently, being completely engrossed in checking the speeds as each solution popped up on the board. In about a half-hour they were all in, and all clipped several minutes from previous tests.

"Excellent, excellent," Dr. Albie pronounced, his face hovering between a smile and a frown. "I'll cut the other half of the board and you can get started immediately. If it takes longer than you expect, stay with it; I'll cover in for the next three days while you catch up on your rest."

Benton forced his mind into safe channels. Once more it had almost run away with him. The completion of his plan was so imminent that already he felt a surge of nostalgia. His work had been exactly to his liking, as no other could ever be; and certainly Dr. Albie, while not a gregarious man, was without peer as a colleague. His strict emotional control and the virtue of carefully weighing many sides of a question before making a decision occasionally irked the more mercurial Benton; but generous compensation was provided in the fact that the doctor leaned over backward rather than take advantage of his position as nominal head of the operating staff of Urei. He rated Benton as his equal, for to the doctor nobody could be inferior by reason of position.

As the afternoon wore on Benton felt his nervous tension mount to heights he had never thought possible. Not, that is, and retain his sanity. Yet he worked coolly, in rigid control of his thoughts every instant. That, of course, and the necessity for trigger alertness as he waited for the sound of the gong, accounted for the rising tension. Benton didn't dare think of his next step; yet he must be ready for it momentarily.

There would be no more than five minutes in which to act when the signal came, and he hadn't as yet allowed the thought of that action to enter his mind! Benton knew that he would do the right thing when the time came; there was no necessity for him to crystallize the thought or to plan the action. Sometime in the half-awake-half-asleep hours he had spent working circuit equations that morning, the plan had reached that stage and he had allowed it to go no further.

He reached a point, at about three o'clock, when it seemed that ten minutes more would bring a complete breakdown of his defense mechanism. Benton never discovered whether he would reach that ultimate for at exactly three someone energized Circuit No. 13 and the gong sounded. As if he hadn't been waiting for that very thing Benton stood paralyzed for several seconds. Then abruptly he sprang into action. Urei was dead at the moment, but he wouldn't stay that way long; and it was during this short interval that Benton must reach the power-house and pull the main switch.

Benton raced along a corridor, tore through a storeroom, ripped frantically at steel doors with a haste that almost dislocated his arms, then fumbled with a bunch of keys as he was confronted by the power-house portal. There were two doors, of course; the first opened upon the anteroom in which was stored the lead armor needed to enter the room containing the atomic pile which furnished Urei's power. Benton ignored the armor standing against the walls. A long stride carried him past it to the alcove in which was set the final door, of massive lead.

Concrete baffles four feet thick lay on the other side and Benton visualized the quick turns he would have to take after he swung open the final door. Time was running out and there wouldn't be another chance; if Benton failed, Urei would be forever on the alert against him—if, indeed, Urei didn't operate on the man's brain forthwith.

There was no hesitation with the key to the second door. It was a large one and quite distinctive. Benton separated it from the others and inserted it in the elongated slot at the left side of the heavy grey door. He turned it sharply, but it resisted. Forcing himself to go slowly he backed it around and tried again. It didn't turn. He took it out, looked at it again, then gave it another try. This time he acted deliberately, certain that the key was inserted properly, but he may as well have used the wrong key, for all the good it did.

Abruptly he stepped back, his face a livid, gargoylish mask. This time he knew where his trouble was.

"You're here!" he accused, speaking to the door.

5

The voice that answered in Benton's brain was gentle. "I didn't mean to punish you that way," it said; "I was busy. But if you remember, I told you I could exist without that building full of electronic apparatus. It was you who assumed I was a liar, you know; I gave you no evidence for the assumption. Look at that key."

Benton was dazed. He seemed to have lost all his drive, his determination to wreck Urei. A reaction was setting in; his hand trembled weakly as he reached for the key and removed it from the slot. He looked at it dully, then let his eyes rest on the bunch from which he had removed it. The large, distinctive key was still with the bunch. The one in his shaking hand was smaller, entirely dissimilar.

"It was better that I let you go this far, anyway," came the silent mental voice. "I was going to let you see this room, sooner or later. Go on in."

Benton's eyes opened a bit wider, but still held the dazed look. The door was swinging wide, by itself. Almost stumbling, he felt his way through the maze of baffles, heedless of the fact that the further he went the more he exposed himself to the deadly, hard rays generated by the pile. Without armor, Benton had intended to enter swiftly, throw the master switch which would kill the pile, then retreat as fast. Now, however, he didn't even think of it. His brain was dulled by defeat after those many hours of rigid control which had been so useless.

But it didn't matter; the pile was already dead.

"This pile was self-maintaining," the voice explained. "It never needed attention, and if something went wrong it would have warned everybody within miles with the sirens. So it's no wonder that nobody ever discovered that I killed it years ago. The thing made me nervous, being so close."

Benton's eyes brightened a little. No amount of letdown could entirely extinguish his scientific curiosity, and this was a mystery he had to solve.

"But you've been operating.... The entire building was powered with this pile. Even the lights...."

There was a mental chuckle. "Sub-cosmic energy does it. I had the technicians hook it up years ago. It's more dependable, also more plentiful, as well as free. Man will discover its use in a few generations, I imagine. Now, my fine friend, if you're temporarily over your murdering rampage, suppose you return to the control room. There's some interesting stuff coming over the television, if you turn it on."

Benton was suddenly aware that the gong had ceased to sound. The defective tube had been replaced and Urei was once again operating. There was no sign of commotion when he came upon his men; they were working on the new circuits, just as he had left them.

"Keep going," he said to the foreman. "If you get stuck, I'll be in the control room. Otherwise keep using the same plans we used this morning."

"We ought to clean up by four," the man answered.

Benton once more heard that chuckle which wasn't quite audible. "Gotta hand it to you," Urei said. "You've got a well-trained crew."

"Yes," thought Benton. "Except that when you boss them, they don't make reports of their work."

"I guess you're talking about this energy-rectifier I just told you about. It wouldn't have paid to let them remember what they made. After all, your science doesn't know enough to understand what it is, or how it works. Also it would have given me away. Don't worry, you'll catch up to it in another generation or six."

"I'm wise to you," Benton reminded. "Why not tell me? It would do humanity a lot of good, you know. And you're supposed to be helping humanity, if I remember correctly."

There was a barely noticeable hesitation. Then: "Let's not discuss it now. I haven't quite made up my mind concerning policy of that sort. I'm still adhering to my rule of answering any question that's asked, within the scope of the knowledge which has been fed to me by man. That leaves your progress up to yourself. And incidentally, I did a little monkeying today which has nothing to do with policy; it was strictly a matter of self-preservation. You'll see what I mean when you turn to that video set."

Benton had entered the control room. He leaned over and fumbled with a shoe lace. "In a minute. You said you guessed I was talking about the energy-rectifier, whatever that is. Didn't you know? Weren't you reading my mind? In fact, weren't you reading it all along and saw through my efforts to disguise my thoughts?"

There was another instant of hesitation. "I see what you're driving at; I should have seen it sooner. As a matter of fact, I did look in on you a couple of times, inasmuch as you were quite distraught about your fantastic idea that I might be going to take over your silly race and run it to suit myself—though I can't see what you figure I might get out of that. And I discovered you were planning today's change-over, which seemed reasonable enough at the time. But once you opened the outer door to the power-house, I should have realized that you had been planning something else.... Congratulations, boy; you fooled me completely. Now turn on that television set, before they get done rehashing the day's events."

Dr. Albie came out of his office, an eyebrow raised questioningly.

"The work's all lined up," Benton explained. "Nothing to do but inspect, when they finish. Thought I'd relieve the monotony by looking at the puppet show."

He snapped on the set, and wasn't surprised to see the familiar face of a news commentator who wasn't due for several hours.

... there can be no doubt of it, he was saying, and it is certainly proof of the efficiency of the now non-existent Iron Curtain. No inkling of this action has reached the western world in spite of the fact that it must have been months in the making. Here Benton heard the eerie chuckle bubbling in his brain. The only mystery lies in the fact that the retired premier allowed the stratagem of rigging the Italian elections to go through, since he had intended to turn over the reins of government to the men now running the Eastern Alliance. Such a thing can only be accounted for by the rigid adherence which the retired premier gave to the plans for conquest laid down by his predecessor. He evidently expected the new government to continue with the same line; we can be thankful it didn't. Peace is now assured.

Dr. Albie's eyes were wide, and so was his mouth. For the moment, at least, he had forgotten his philosophy. Benton was intently watching the face on the screen, his own revealing nothing.

But whatever the reasons, the voice continued, it is too late to change policy back to what it has been. The acclaim of the peoples of the Eastern Alliance has been too great for any reversal to take place. They have shown their approval of the new elections to be held in Italy next week, but most of all they have rejoiced at the removal of the Iron Curtain and all it implies. It will now be possible for a subject of the Alliance to travel as he wishes, read what he wishes and listen to western broadcasts without having his set seized by the police and his life placed in jeopardy. Folks, we are entering a new era....

Dr. Albie came completely out of his shell. "Man!" he shouted. "This is history! If nothing happens to spoil it we'll have a world government in a matter of a few years.... Where are you going?"

Benton stopped and forced a smile which wasn't hard coming. "I just thought of something I forgot to tell the men. Be back shortly. This will require some talking over, but right now there's a job to be done."

The master physicist watched him leave the control room, his jaw slack. "And I thought I was the reserved one," he muttered.

Safely out of the control room and out of sight of any of the technicians, Benton sat down. There was no chair, so he sat on the floor; his knees, it seemed, had become a bit wobbly again.

"So now you're convinced," Urei said. "You ignore all the sensible, logical reasons which exist to prove I'm not inimical. And for a reason which is really no reason at all, you decide to believe me. I merely manipulated a few Russians and Bulgarians to prevent a war which would have wrecked my body. Purely a matter of self-preservation. I'm not so sure I'd have bothered if my person hadn't been threatened; after all, it's no business of mine if man wants to annihilate himself."

Benton was grinning. "You're a fraud," he said. "You already know more than all mankind put together; and I'll bet you didn't use any of our material to solve the problem of converting sub-cosmic energy to a usable form."

"Some, some. But not much, I'll admit."

"So what do you want with the knowledge stored in the mechanical bank of memory cells we've provided you? You need it like I need a hole in the head. I can only conclude that you've stopped the impending war because you don't want mankind destroyed. You can do things for yourself without those cells and all this machinery; all you use it for is to solve the problems we pose for you. Incidentally, I suspect that your motivations are still the ones which humans originally built into you, whether you like it or not."

"Could be. Or maybe I retain them because they agree with me. I might change my mind, you know; I might get tired of nursemaiding and decide to annihilate your entire race. Heh, Heh. Seems like a good idea, now that I think of it."

Benton laughed. "You won't; you're in a rut. And even if you did get tired, you'd merely let us shift for ourselves, which we're used to doing anyway."

"Nonsense. I'd probably reason that since the ape animal has made such a botch of his head start in the evolutionary race for rational thinking, it might not be a bad idea to give some other animal a start. Ursus Proper might be a good place to begin."

"Bears are foolish by nature," Benton countered.... "It wouldn't matter what form of life you chose anyway; they'd all have to go through the same stages, being without exception governed by thalamic reactions. That's the thing you object to in man, and since your new candidate would have to go through the same lengthy business of developing cortical ascendancy, you'll have none of it. So quit kidding around; I've reached a nonthalamic conclusion."

"And you're stuck with it. I knew it would happen. That's why I didn't use you and leave your memory blank; with your head working on my side, you'll be useful."

Benton knew when he had something. "That'll work two ways," he said. "First I want you to dive inside my skull and tell me something. I'm holding out for a bargain, you know. What is the bargain?"

As he spoke, Benton concentrated upon the problem of reasoning out the location of Urei's sub-cosmic converter. He didn't have far to go for an answer. A few years ago somebody had noticed a radiation leak on one side of the power-house, near a spot where the power cables came through the walls of the massive building. Now it happened that there were taps from those cables, less than a hundred yards away. That made it likely that the converter had been placed somewhere before the taps. The only place that could be would be either inside the power-house or inside the wall itself. Therefore Urei had caused the repairmen and technicians to place his machine inside the very wall they had been reinforcing. In no other way could it have escaped notice and investigation.

"I can't read it if you don't think about it," Urei complained; "you guessed right about the converter, though."

Benton nodded. "Then last night you didn't get anything from me at all?"

If a disembodied voice can sound shamefaced, Urei's did. "All right, so I lied; but you annoyed me with your stubbornness."

"Ah. Thalamic reactions."

"I've been in bad company," Urei defended. "What I wanted from you was the assurance that the people of the Eastern Alliance were essentially the same as the humans I've met. I had to know if their reactions to my manipulations would be similar, before I acted. Most of the stuff I've been able to read about them led me to believe they were entirely different. If so, I couldn't be sure of results."

"They're similar, of course," Benton said. "They differ only in that they have been indoctrinated to believe a lot of things which aren't so. So have we, for that matter—to a different degree and on different subjects. But essentially we're the same species of animal and react alike to stimuli. But you didn't get that information from me, eh?"

"No. I relied on abstract reasoning and got the right answer. It's tricky business, though. I might have precipitated things, instead of preventing them. Ordinarily I could have obtained that information from a human brain, if it knew the right answer, by guiding the subject's thought into the right channel. I can't read thoughts that aren't there, you know. That's the trouble I had with you; about the only control I had over you was confined to your motor centers. I could make you turn a page or select the wrong key, but I couldn't keep you from knowing about it. In fact it was the very trouble I had with you which made me doubt that humans were as alike as I had assumed. And also what made me decide that I needed you to keep me straight in my relations with humans in general.

"I reason from facts alone, you know. And from the facts at hand I have decided that your bargain is going to consist of demanding the knowledge necessary for you to make a sub-cosmic energy converter, in return for your help in making me understand the obscure psychology of humans and their incomprehensible motivations." There was a protracted mental shudder here. "And I suppose you'll keep that up as long as you live. O.K. But you can expect an argument every time."

Benton went back into the control room with a smile that raised that quizzical eyebrow on Dr. Albie's now serene face. The good doctor couldn't know that his assistant's mind was as far from the recent world-shaking news as it was from the business of the new control circuits. His eyebrow went up another thirty-second of an inch when Benton, apparently musing, said: "A mind is inviolate so long as it refuses to broadcast. I refuse to broadcast. Q.E.D."