Alice: But I don't want to go among mad people.
The Cat: Oh, you can't help that. We're all mad here. I'm mad. You're mad.
Alice: How do you know I'm mad?
The Cat: You must be. Or you wouldn't have come here.
Alice: And how do you know that you're mad?
The Cat: To begin with, a dog's not mad. You grant that?
Alice: I suppose so,
The Cat: Well, then, 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.