"So there is a change from day to night!" "I didn't say that. The stars simply shine at night. Why should they shine during the day when the world wants them to shine only at night?" "Once they shone all the time." "Naturally," said Crifer, becoming interested. "They are variable." * * * * * Rikud regretted that he never had had the chance to read that book on astronomy. He hadn't been reading too much lately. The voice of the reading machine had begun to bore him. He said, "Well, variable or not, our whole perspective has changed." And when Chuls looked away in disinterest, Rikud became angry. If only the man would realize! If only anyone would realize! It all seemed so obvious. If he, Rikud, walked from one part of the world to another, it was with a purpose--to eat, or to sleep, or perhaps to bathe in the health-rays. Now if the world had walked from--somewhere, through the vast star-speckled darkness and to the great garden outside, this also was purposeful. The world had arrived at the garden for a reason. But if everyone lived as if the world still stood in blackness, how could they find the nature of that purpose? "I will eat," Chuls said, breaking Rikud's revery. Damn the man, all he did was eat! Yet he did have initiative after a sort. He knew when to eat. Because he was hungry. And Rikud, too, was hungry. Differently. * * * * * He had long wondered about the door in the back of the library, and now, as Crifer sat cross-legged on one of the dusty tables, reading machine and book on astronomy or stars in his lap, Rikud approached the door. "What's in here?" he demanded. "It's a door, I think," said Crifer. "I know, but what's beyond it?" "Beyond it? Oh, you mean _through_ the door." "Yes." "Well," Crifer scratched his head, "I don't think anyone ever opened it. It's only a door." "I will," said Rikud. "You will what?" "Open it. Open the door and look inside." A long pause. Then, "Can you do it?" "I think so." "You can't, probably. How can anyone go where no one has been before? There's nothing. It just isn't. It's only a door, Rikud." "No--" Rikud began, but the words faded off into a sharp intake of breath. Rikud had turned the knob and pushed. The door opened silently, and Crifer said, "Doors are variable, too, I think." Rikud saw a small room, perhaps half a dozen paces across, at the other end of which was another door, just like the first. Halfway across, Rikud heard a voice not unlike that of the reading machine. He missed the beginning, but then: