“They’re cheering for you,” she said with a smile. 
  “But I could never have done it,” [Milo] objected, “without everyone else’s help.”
  “That may be true,” said Reason gravely, “but you had the courage to try; 
     and what you can do is often simply a matter of what you will do.”
  “That’s why,” said King Azaz, “there was one very important thing about your quest 
     that we couldn’t discuss until you returned.”
  “I remember,” said Milo eagerly. “Tell me now.”
  “It was impossible,” said the king, looking at the Mathemagician.
  “Completely impossible,” said the Mathemagician, looking at the king.
  “Do you mean … ,” said the bug, who suddenly felt a bit faint.
  “Yes, indeed,” they repeated together, “but if we’d told you then, you might not have gone … 
    and, as you’ve discovered, so many things are possible just as long as you don’t know they’re impossible.”

- The Phantom Tollbooth (1961)