`In THAT direction,' the Cat said, waving its right paw round, `lives a Hatter: and in THAT direction,' waving the other paw, `lives a March Hare. Visit either you like: they're both mad.'
`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.'
Alice didn't think that proved it at all; however, she went on `And how do you know that you're mad?'
`To begin with,' said the Cat, `a dog's not mad. You grant that?'
`I suppose so,' said Alice.
`Well, then,' the Cat went on, `you see, a dog growls when it's angry, and wags its tail when it's pleased. Now I growl when I'm pleased, and wag my tail when I'm angry. Therefore I'm mad.'
- Lewis Carroll,
Alice and the Cheshire Cat, Alice’s Adventures in Wonderland