At the foot of the ramp, the quiet voice redirected Alvin, and he walked between an avenue of sleeping titan shapes. Three times the voice spoke to him again, until presently he knew that he had reached his goal.
The machine before which he was standing was smaller than most of its companions, but he felt dwarfed as he stood beneath it. The five tiers with their sweeping horizontal lines gave the impression of some crouching beast, and looking from it to his own robot Alvin found it hard to believe that both were products of the same evolution, and both described by the same word.
About three feet from the ground a wide transparent panel ran the whole length of the structure. Alvin pressed his forehead agaipst the smooth, curiously warm material and peered into the machine. At first he saw nothing then, by shielding his eyes, he could distinguish thousands of faint points of light hanging in nothingness. They were ranged one beyond the other in a three-dimensional lattice, as strange and as meaningless to him as the stars must have been to ancient man. Though he watched for many minutes, forgetful of the passage of time, the colored lights never moved from their places and their brilliance never changed.
If he could look into his own brain, Alvin realized, it would mean as little to him. The machine seemed inert and motionless because he could not see its thoughts.
For the first time, he began to have some dim understanding of the powers and forces that sustained the city. All his life he had accepted without question the miracle of the synthesizers which age after age provided in an unending stream all the needs of Diaspar. Thousands of times he had watched that act of creation, seldom remembering that somewhere must exist the prototype of that which he had seen come into the world.
As a human mind may dwell for a little while upon a single thought, so the infinitely greater brains which were but a portion of the Central Computer could grasp and hold forever the most intricate ideas. The patterns of all created things were frozen in these eternal minds, needing only the touch of a human will to make them reality.
The world had indeed gone far since, hour upon hour, the first cavemen had patiently chipped their arrowheads and knives from the stubborn stone.
Alvin waited, not caring to speak until he had received some further sign of recognition. He wondered how the Central Computer was aware of his presence, and could see him and hear his voice. Nowhere were there any signs of sense organs-none of the grilles or screens or emotionless crystal eyes through which robots normally had knowledge of the world around them.
«State your problem,» said the quiet voice in his ear. It seemed strange that this overwhelming expanse of machinery should sum up its thoughts so softly. Then Allvin realized that he was flattering himself; perhaps not even a millionth part of the Central Computer’s brain was dealing with him.
He was just one of the innumerable incidents that came to its simultaneous attention as it watched over Diaspar. It was hard to talk to a presence who filled the whole of the space around you. Alvin’s words seemed to die in the empty air as soon as he had uttered them.
«What am I?» he asked.
If he had put that question to one of the information machines in the city, he knew what the reply would have been. Indeed, he had often done so, and they had always answered, «You are a Man.» But now he was dealing with an intelligence of an altogether different order, and there was no need for painstaking semantic accuracy. The Central Computer would know what he meant, but that did not mean that it would answer him.
Indeed, the reply was exactly what Alvin had feared.
«I cannot answer that question. To do so would be to reveal the purpose of my builders, and hence to nullify it.»
«Then my role was planned when the city was laid down?»
«That can be said of all men.»
This reply made Alvin pause It was true enough; the human inhabitants of Diaspar had been designed as carefully as its machines. The fact that he was a Unique gave Alvin rarity, but there was no necessary virtue in that.
He knew that he could learn nothing further here regarding the mystery of his origin. It was useless to try to trick this vast intelligence, or to hope that it would disclose information it had been ordered to conceal. Alvin was not unduly disappointed; he felt that he had already begun to glimpse the truth, and in any case this was not the main purpose of his visit.
He looked at the robot he had brought from Lys, and wondered bow to make his next step. It might react violently if it knew what he was planning, so it was essential that it should not overhear what he intended to say to the Central Computer.
«Can you arrange a zone of silence?» he asked.
Instantly, be sensed the unmistakable «dead» feeling, the total blanketing of all sounds, which descended when one was inside such a zone. The voice of the Computer, now curiously flat and sinister, spoke to him: «No one can hear us now. Say what you wish.»
Alvin glanced at the robot; it bad not moved from its position. Perhaps it suspected nothing, and he had been quite wrong in ever imagining that it had plans of its own. It might have followed him into Diaspar like a faithful, trusting servant, in which case what he was planning now seemed a particularly churlish trick.
«You have heard bow I met this robot,» Alvin began. «It must possess priceless knowledge about the past, going back to the days before the city as we know it existed. It may even be able to tell us about the other worlds than Earth, since it followed the Master on his travels. Unfortunately, its speech circuits are blocked. I do not know how effective that block is, but I am asking you to clear it.»
His voice sounded dead and hollow as the zone of silence absorbed every word before it could form an echo. He waited, within that invisible and unreverberant void, for his request to be obeyed or rejected.
«Your order involves two problems,» replied the Computer. «One is moral, one technical. This robot was designed to obey the orders of a certain man. What right have I to override them, even if I can?»
It was a question which Alvin had anticipated and for which he had prepared several answers.
«We do not know what exact form the Master’s prohibition took,» be replied. «If you can talk to the robot, you may be able to persuade it that the circumstances in which the block was imposed have now changed.»
It was, of course, the obvious approach. Alvin had attempted it himself, without success, but he hoped that the Central Computer, with its infinitely greater mental resources, might accomplish what he had failed to do.
«That depends entirely upon the nature of the block,» came the reply. «It is possible to set up a block which, if tampered with, will cause the contents of the memory cells to be erased. However, I think it unlikely that the Master possessed sufficient skill to do that; it requires somewhat specialized techniques. I will ask your machine if an erasing circuit has been set up in its memory units.»
«But suppose,» said Alvin in sudden alarm, «it causes erasure of memory merely to ask if an erasing circuit exists?»
«There is a standard procedure for such cases, which I shall follow. I shall set up secondary instructions, telling the machine to ignore my question if such a situation exists. It is then simple to insure that it will become involved in a logical paradox, so that whether it answers me or whether it says nothing it will be forced to disobey its’ instructions. In such . an event all robots act in the same manner, for their own protection. They clear their input circuits and act as if no question has been asked.»