The City and the Stars Page 0,17

of separate cultures and civilizations which endured for a little while and then perished. How did Diaspar achieve its extraordinary stability?"

Alvin was surprised that anyone should ask so elementary a question, and his hopes of learning something new began to wane.

"Through the Memory Banks, of course," he replied. "Diaspar is always composed of the same people, though their actual groupings change as their bodies are created or de-stroyed."

Khedron shook his head. "That is only a very small part of the answer. With exactly the same people, you could build many different patterns of society. I can't prove that, and I've no direct evidence of it, but I believe it's true. The designers of the city did not merely fix its population; they fixed the laws governing its behavior. We're scarcely aware that those laws exist, but we obey them. Diaspar is a frozen culture, which cannot change outside of narrow limits. The Memory Banks store many other things outside the patterns of our bodies and personalities. They store the image of the city itself, holding its every atom rigid against all the changes that time can bring. Look at this pavement-it was laid down millions of years ago, and countless feet have walked upon it. Can you see any sign of wear? Unprotected matter, however adamant, would have been ground to dust ages ago. But as long as there is power to operate the Memory Banks, and as long as the matrices they contain can still control the patterns of the city, the physical structure of Diaspar will never change."

But there have been some changes," protested Alvin. "Many buildings have been torn down since the city was built, and new ones erected."

"Of course-but only by discharging the information stored in the Memory Banks and then setting up new patterns. In any case, I was merely mentioning that as an example of the way the city preserves itself physically. The point I want to make is that in the same way there are machines in Diaspar that preserve our social structure. They watch for any changes, and correct them before they become too great. How do they do it? I don't know-perhaps by selecting those who emerge from the Hall of Creation. Perhaps by tampering with our personality patterns we may think we have free will, but can we be certain of that?"

"In any event, the problem was solved. Diaspar has survived and come safely down the ages, like a great ship carrying as its cargo all that is left of the human race. It is a tremendous achievement in social engineering, though whether it is worth doing is quite another matter.

"Stability, however, is not enough. It leads too easily to stagnation, and thence to decadence. The designers of the city took elaborate steps to avoid this though these deserted build-ings suggest that they did not entirely succeed. I, Khedron the Jester, am part of that plan. A very small part, perhaps. I like to think otherwise, but I can never be sure."

"And just what is that part?" asked Alvin, still very much is the dark, and becoming a little exasperate.

"Let us say that I introduce calculated amounts of disorder into the city. To explain my operations would be to destroy their effectiveness. Judge me by my deeds, though they are few, rather than my words, though they are many."

Alvin had never before met anyone quite like Khedron. The Jester was a real personality-a character who stood head and shoulders above the general level of uniformity which was typical of Diaspar. Though there seemed no hope of discovering precisely what his duties were and how he carried them out, that was of minor importance. All that mattered, Alvin sensed, was that here was someone to whom he could talk-when there was a gap in the monologue-and who might give him answers to many of the problems that had puzzled him for so long.

They went back together down through the corridors of the Tower of Loranne, and emerged beside the deserted moving way. Not until they were once more in the streets did it occur to Alvin that Khedron had never asked him what he had been doing out here at the edge of the unknown. He suspected that Khedron knew, and was interested but not surprised. Something told him that it would be very difficult to surprise Khedron.

They exchanged index numbers, so that they could call each other whenever they wished. Alvin was anxious to see more of the Jester, though