"Here," he said, handing her a book. "Try to read this with your eyes shut."
"What? That's impossible," she replied.
"No, it's definitely possible to read a book with your eyes shut."
"No it isn't. How can you read without seeing the words?"
"No, you can't. It's not possible to read ANY book with your eyes shut."
"Yes, any book!"
"Care to make a wager? I bet you I can read a book with my eyes shut."
"Pfffft, easy money. You're on."
Having trapped her neatly, he grinned, and pulled out a book written entirely in Braille.