 What struggle does the door in the library represent?
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. 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. "Yes?" Almost no one read any more, and the library was heavy with the smell of dust.
 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.