"But I don't want to go among mad people,"
Alice remarked.
"Oh, you can't help that,"
said the Cat:
"We're all mad here. I'm mad. You're mad."
"How do you know I'm mad?"
said Alice.
"You must be," said the Cat,
"or you wouldn't have come here."


 
(Lewis Carroll,
"Alice's adventures in Wonderland", 1865)