 What is not a theme explored in this story?
When nobody aboard ship remembers where it's going, how can they tell when it has arrived? 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. 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. 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. There had been a revolt—again a term without any real meaning, a term that could have no reality outside of the reading machine—and the elders were overthrown. The people had decided that they did not know where they were going, or why, and that it was unfair that the elders alone had this authority. Much of this Rikud could not understand, but he knew enough to realize that the reading machine had sided with the people against the elders, and it said the people had won. True, this was the only case of its kind, the exception to the rule, but it proved the world was not perfect. "Variability," he told them, "is a contradictory term. Except that it was variable, which was like change, being tied up somehow with age.
 Equality must be realized.
 Change is necessary and inevitable for survival.  Fear is a powerful motivator.  Perception can often be all-encompassing.  Equality must be realized.