 What struggle does the door in the library represent?
Extensive research did not uncover any evidence that the U.S. copyright on this publication was renewed.] When nobody aboard ship remembers where it's going, how can they tell when it has arrived? Every day for a week now, Rikud had come to the viewport to watch the great changeless sweep of space. But ever since the engines somewhere in the rear of the world had changed their tone, from the steady whining Rikud had heard all twenty-five years of his life, to the sullen roar that came to his ears now, the feelings had grown. And, because he had realized this odd difference in himself, he kept it locked up inside him. Instead, there was more of the blackness, and one very bright star set apart by itself in the middle of the viewport. Someone was clomping up the companionway behind Rikud. "In five more years," the older man chided, "you'll be ready to sire children. But it came again, and each time it left him with a feeling he could not explain. Rikud knew that something which he could not explain had entered the elder man's head for a moment, but it had departed almost before Chuls knew of its existence. Perhaps two score men lay about, naked, under the ray tubes. There was a strange thought, and Rikud's brain whirled once more down the tortuous course of half-formed questions and unsatisfactory answers. Once, here in this same ray room, he had had the impulse to hurl himself head-first against the wall, just to see what would happen. But something soft had cushioned the impact—something which had come into being just for the moment and then abruptly passed into non-being again, something which was as impalpable as air. Rikud had been stopped in this action, although there was no real authority to stop him.
 The struggle for Rikud and all the others to conceptualize what they don't know or haven't seen before.
 The struggle between man and machine, and the power machine now has over them.  The struggle for Rikud and all the others to conceptualize what they don't know or haven't seen before.  Rikud's fear of what's behind it.  The struggle between authority and the people it runs.