ZZ One fastened a look of suspicion on the Jovian and clicked out, 'Would it be all right if I went in and looked around? I am very interested in this.'

  Three said, 'You're being childish, One. They're telling the truth. Oh well, nose around if you must. But don't take too long; we've got to move on.'

  The Jovian said, 'You have no understanding of the heat involved. You will die.'

  'Oh no,' explained One casually. 'Heat doesn't bother us.'

  There was a Jovian conference, and then a scene of scurrying confusion as the life of the factory was geared to this unusual emergency. Screens of heat-absorbent material were set up, and then a door dropped open, a door that had never before budged while the forges were working. ZZ One entered and the door closed behind him. Jovian officials crowded to the transparent areas to watch.

  ZZ One walked to the nearest forge and tapped the out­side. Since he was too short to see into it comfortably, he tipped the forge until the molten metal licked at the lip of the container. He peered at it curiously, then dipped his hand in and stirred it awhile to test the consistency. Having done this, he withdrew his hand, shook off some of the fiery metallic droplets and wiped the rest on one of his six thighs. Slowly he went down the line of forges, then sig­nified his desire to leave.

  The Jovians retired to a great distance when he came out of the door and played a stream of ammonia on him, which hissed, bubbled and steamed until he was brought to bear­able temperature once more.

  ZZ One ignored the ammonia shower and said, 'They were telling the truth. No force fields.'

  Three began, 'You see———' but One interrupted im­patiently, 'But there's no use delaying. The human masters instructed us to find out everything and that's that.'

  He turned to the Jovian and clicked out, without the slightest hesitation, 'Listen, has Jovian science developed force fields?'

  Bluntness was, of course, one of the natural consequences of One's less well developed mental powers. Two and Three knew that, so they refrained from expressing dis­approval of the remark.

  The Jovian official relaxed slowly from his strangely stiffened attitude which had somehow given the impression that he had been staring stupidly at One's hand—the one he had dipped into the molten metal. The Jovian said slowly, 'Force fields? That, then, is your main object of curiosity?'.

  'Yes,' said One with emphasis.

  There was a sudden and patent gain in confidence on the Jovian's part, for the clicking grew sharper. 'Then come, vermin!'

  Whereupon Three said to Two, 'We're vermin again, I see—which sounds as if there's bad news ahead.' And Two gloomily agreed.

  It was to the very edge of the city that they were now led—to the portion which on Earth would have been termed the suburbs—and into one of a series of closely integrated structures, which might have corresponded vaguely to a terrestrial university.

  There were no explanations, however, and none was asked for. The Jovian official led the way rapidly, and the robots followed with the grim conviction that the worst was just about to happen.

  It was ZZ One who stopped before an opened wall section after the rest had passed on. 'What's this?' he wanted to know.

  The room was equipped with narrow, low benches, along which Jovians manipulated rows of strange devices, of which strong, inch-long electromagnets formed the prin­cipal feature.

  'What's this?' asked One again.

  The Jovian turned back and exhibited impatience. 'This is a students' biological laboratory. There's nothing there to interest you.'

  'But what are they doing?'

  'They are studying microscopic life. Haven't you ever seen a microscope before?'

  Three interrupted in explanation, 'He has, but not that type. Our microscopes are meant for energy-sensitive organs and work by refraction of radiant energy. Your microscopes evidently work on a mass-expansion basis. Rather ingenious.'

  ZZ One said, 'Would it be all right if I inspected some of your specimens?'

  'Of what use will that be? You cannot use our micro­scopes because of your sensory limitations and it will simply force us to discard such specimens as you approach for no decent reason.'

  'But I don't need a microscope,' explained One, with surprise. 'I can easily adjust myself for microscopic vision.'

  He strode to the nearest bench, while the students in the room crowded to the corner in an attempt to avoid con­tamination. ZZ One shoved a microscope aside and in­spected the slide carefully. He backed away, puzzled, then tried another… a third… a fourth.

  He came back and addressed the Jovian. 'Those are supposed to be alive, aren't they? I mean those little worm things.'

  The Jovian said, 'Certainly.'

  "That's strange—when I look at them, they die!'

  Three exclaimed sharply and said to his two companions, 'We've forgotten our gamma-ray radiation. Let's get out of here, One, or we'll kill every bit of microscopic life in the room.'

  He turned to the Jovian, 'I'm afraid that our presence is fatal to weaker forms of life. We had better leave. We hope the specimens are not too difficult to replace. And, while we're about it, you had better not stay too near us, or our radiation may affect you adversely. You feel all right so far, don't you?' he asked.

  The Jovian led the way onward in proud silence, but it was to be noticed that thereafter he doubled the distance he had hitherto kept between himself and them.

  Nothing more was said until the robots found themselves in a vast room. In the very center of it huge ingots of metal rested unsupported in mid-air—or, rather, supported by nothing visible—against mighty Jovian gravity.

  The Jovian clicked, 'There is your force field in ultimate form, as recently perfected. Within that bubble is a vacuum, so that it is supporting the full weight of our atmo­sphere plus an amount of metal equivalent to two large spaceships. What do you say to that?'

  'That space travel now becomes a possibility for you,' said Three.

  'Definitely. No metal or plastic has the strength to hold our atmosphere against a vacuum, but a force field can— and a force-field bubble will be our spaceship. Within the year we will be turning them out by the hundreds of thou­sands. Then we will swarm down upon Ganymede to de­stroy the verminous so-called intelligences that attempt to dispute our dominion of the universe.'

  'The human beings of Ganymede have never attempted———' began Three, in mild expostulation.

  'Silence!' snapped the Jovian. 'Return now and tell them what you've seen. Their own feeble force fields—such as the one your ship is equipped with—will not stand against us, for our smallest ship will be a hundred times the size and power of yours.'

  Three said, 'Then there's nothing more to do and we will return, as you say, with the information. If you could lead us back to our ship, we'll say good-bye. But by the way, just as a matter for the record, there's something you don't understand. The humans of Ganymede have force fields, of course, but our particular ship isn't equipped with one. We don't need any.'

  The robot turned away and motioned his companions to follow. For a moment they did not speak, then ZZ One muttered dejectedly, 'Can't we try to destroy this place?'

  'It won't help,' said Three. 'They'd get us by weight of numbers. It's no use. In an earthly decade the human masters will be finished. It is impossible to stand against Jupiter. There's just too much of it. As long as Jovians were tied to the surface, the humans were safe. But now that they have force fields———All we can do is to bring the news. By the preparation of hiding places, some few may survive for a short while.'

  The city was behind them. They were out on the open plain by the lake, with their ship a dark spot on the horizon, when the Jovian spoke suddenly :

  'Creatures, you say you have no force field?'

  Three replied without interest, 'We don't need one.'

  'How then does your ship stand the vacuum of space without exploding because of the atmospheric pressure within?' And he moved a tentacle as if in mute gesture at the Jovi
an atmosphere that was weighing down upon them with a force of twenty million pounds to the square inch.

  'Well,' explained Three, 'that's simple. Our ship isn't airtight. Pressures equalize within and without.'

  'Even in space? A vacuum in your ship? You lie!'

  'You're welcome to inspect our ship. It has no force field and it isn't airtight. What's marvelous about that? We don't breathe. Our energy is obtained through direct atomic power. The pressure or absence of air pressure makes little difference to us and we're quite at home in a vacuum.'

  'But absolute zero!'

  'It doesn't matter. We regulate our own heat. We're not interested in outside temperatures.' He paused. 'Well, we can make our own way back to the ship. Good-bye. We'll give the humans of Ganymede your message—war to the end!'

  But the Jovian said, 'Wait! I'll be back.' He turned and went toward the city.

  The robots stared, and then waited in silence.

  It was three hours before he returned and when he did, it was in breathless haste. He stopped within the usual ten feet of the robots, but then began inching his way forward in a curious groveling fashion. He did not speak until his rubbery gray skin was almost touching them, and then the radio code sounded, subdued and respectful.

  'Honored sirs, I have been in communication with the head of our central government, who is now aware of all the facts, and I can assure you that Jupiter desires only peace.'

  'I beg your pardon?' asked Three blankly.

  The Jovian drove on hastily. 'We are ready to resume communication with Ganymede and will gladly promise to make no attempt to venture into space. Our force field will be used only on the Jovian surface.'

  'But———' Three began.

  'Our government will be glad to receive any other representatives our honorable human brothers of Ganymede would care to send. If your honors will now condescend to swear peace———' a scaly tentacle swung out toward them and Three, quite dazed, grasped it. Two and One did like­wise as two more were extended to them.

  The Jovian said solemnly: 'There is then eternal peace between Jupiter and Ganymede.'

  The spaceship which leaked like a sieve was out in space again. The pressure and temperature were once more at zero, and the robots watched the huge but steadily shrink­ing globe that was Jupiter.

  'They're definitely sincere,' said ZZ Two, 'and it's very gratifying, this complete about-face, but I don't get it.'

  'It is my idea,' observed ZZ One, 'that the Jovians came to their senses just in time and realized the incredible evil involved in the thought of harm to a human master. That would be only natural.'

  ZZ Three sighed and said, 'Look, it's all a matter of psychology. Those Jovians had a superiority complex a mile thick and when they couldn't destroy us, they were bound to save face. All their exhibitions, all their explana­tions, were simply a form of braggadocio, designed to impress us into the proper state of humiliation before their power and superiority.'

  'I see all that,' interrupted Two, 'but———'

  Three went on, 'But it worked the wrong way. All they did was to prove to themselves that we were stronger, that we didn't drown, that we didn't eat or sleep, that molten metal didn't hurt us. Even our very pressure was fatal to Jovian life. Their last trump was the force field. And when they found out that we didn't need them at all, and could live in a vacuum at absolute zero, they broke.' He paused and added philosophically, 'When a superiority complex like that breaks, it breaks all the way.'

  The other two considered that, and then Two said, 'But it still doesn't make sense. Why should they care what we can or can't do? We're only robots. We're not the ones they have to fight.'

  'And that's the whole point, Two,' said Three softly. 'It's only after we left Jupiter that I thought of it. Do you know that through an oversight, quite unintentionally, we neg­lected to tell them we were only robots.'

  'They never asked us,' said One.

  'Exactly. So they thought we were human beings and that all the other human beings were like us!'

  He looked once more at Jupiter, thoughtfully. 'No won­der they decided to quit!'

  Part Two

  The Laws of Robotics

  Neither Robot AL-76 nor Robot ZZ-3 represented the mainstream of my thinking. As a matter of fact, I had started correctly with my very earliest robot story, 'Robbie,' which appeared in the September 1940 Super Science Stories (under the editorially chosen, and to me personally distasteful, title of 'Strange Playfellow').

  'Robbie' dealt with a rather primitive robot model, one that was unable to speak. It was designed to fulfill the task of nursemaid and to fulfill it admirably. Far from being a threat to human beings or wanting to destroy its creator or to take over the world, it strove only to do what it was designed to do. (Does an automobile want to fly? Does an electric light bulb want to type letters?)

  1 trod this path in eight other stories written during the 1940s, all of which appeared in Astounding Science Fic­tion. They were:

  'Reason,' April 1941 'Liar!,' May 1941 'Runaround,' March 1942 'Catch That Rabbit,' February 1944 'Paradoxical Escape,' August 1945 'Evidence,' September 1946 'Little Lost Robot,' March 1947 'The Evitable Conflict,' June 1950

  These eight stories plus 'Robbie' were brought together in a collection entitled I, Robot, which was published by Gnome Press in 1950. After the usual reprint and foreign editions, it was allowed to go out of print, whereupon the enterprising gentlemen of Doubleday & Company, recog­nizing a Good Thing, arranged to bring out a new edition in 1963 (Because of the recent appearance of this collection, it is not being included in this otherwise definitive collection of my robot stories. The discerning reader will now understand why this book is entitled The Rest of the Robots.)

  My sensible, non-Mephistophelean robots were not really brand-new. There had been occasional robots of this type before 1940. Indeed, we can find some robots, designed to fulfill a reasonable purpose without trouble and without danger, in the Iliad. In Book XVIII of that epic, Thetis visits the smith-god, Hephaistos, in order to obtain divinely forged armor for her son, Achilles. Hephaistos is lame and walks with difficulty. There is the passage (in the translation of W. H. D. Rouse) which describes how he comes out to meet Thetis:

  'Then he… limped out leaning on a thick stick, with a couple of maids to support him. These are made of gold exactly like living girls; they have sense in their heads, they can speak and use their muscles, they can spin and weave and do their work…'

  In short, they were robots.

  And yet, though I wasn't the first in the field by the not-so-narrow margin of 2500 years, I managed to build enough consistent background into my stories to gain for myself the reputation of having created the 'modern robot story.'

  Gradually, story by story, I evolved my notions on the subject. My robots had brains of platinum-iridium sponge and the 'brain paths' were marked out by the production and destruction of positrons. (No, I don't know how this is done.) As a result it is as the 'positronic robots' that my creatures came to be known.

  To design the positronic brains of my robots required a huge and intricate new branch of technology to which I gave the name 'robotics.' To me it seemed a natural word, as natural as 'physics' or 'mechanics.' However, rather to my surprise, it turned out to be an invented word and is not to be found in either the second or third edition of Web­ster's Unabridged.

  Most important of all, 1 made use of what I called 'The Three Laws of Robotics,' which were intended to place in words the basic design of the robot brains, a basic design to which all else was subsidiary.

  These laws are:

  1. A robot may not injure a human being, or, through inaction, allow a human being to come to harm.

  2. A robot must obey the orders given it by human beings except where such orders would conflict with the First Law.

  3. A robot must protect its own existence as long as such protection does not conflict with the First or Second Law.

  Apparently i
t is these laws of robotics (first stated ex­plicitly in 'Runaround') that have done most to change the nature of the robot stories in modern science fiction. It is rare that a robot of the old turning-on-its-creator type will be found between the pages of the better science-fiction magazines, simply because that would violate the First Law. Many writers of robot stories, without actually quot­ing the three laws, take them for granted and expect the readers to do the same.

  In fact I have been told that if, in future years, I am to be remembered at all, it will be for these three laws of robotics. In a way this bothers me, for I am accustomed to thinking of myself as a scientist, and to be remembered for the non-existent basis of a non-existent science is embarras­sing. Yet if robotics ever does reach the pitch of excellence described in my stories, it may be that something like the Three Laws will really come into existence and, if so, I will have achieved a rather unusual {if, alas, posthumous) triumph.

  My positronic robot stones fall into two groups; those that concern Dr. Susan Calvin and those that do not. Those that do not, often deal with Gregory Powell and Mike Donovan, who were constantly field-testing experimental robots and, just as constantly, running into trouble with them. There was just enough ambiguity in the Three Laws to provide the conflicts and uncertainties required for new stories, and, to my great relief, it seemed always to be pos­sible to think up a new angle out of the sixty-one words of the Three Laws.

  Four stories in I, Robot dealt with Powell and Donovan. After that book was published, exactly one other such story was published, or rather a story about Donovan alone. Once again I was being funny at the expense of my robots, but this time it wasn't I that was telling the story, it was Donovan, and I am not responsible for him.

  The story, 'First Law,' appeared in the October 1956 issue of Fantastic Universe Science Fiction.

  FIRST LAW

  Mike Donovan looked at his empty beer mug, felt bored, and decided he had listened long enough. He said, loudly, 'If we're going to talk about unusual robots, I once knew one that disobeyed the First Law.'