“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.”
Source: Alice in Wonderland
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Lewis Carroll 241
English writer, logician, Anglican deacon and photographer 1832–1898Related quotes
“I'm not mad that you got mad when I got mad when you said I should go drop dead.”
tick, tick... BOOM! (1990)

Source: Alice in Wonderland: Based on the Motion Picture Directed by Tim Burton

“Alice: This is impossible.
The Mad Hatter: Only if you believe it is.”

3 October 2016 Facebook post https://www.facebook.com/hon.maximebernier/posts/10154565323228703 quoted 28 May 2018 on Toronto Sun https://torontosun.com/opinion/columnists/bonokoski-mad-maxs-dustup-over-a-liberal-mps-skin-colour-comments
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Tales of Three Hemispheres http://www.gutenberg.net/dirs/1/1/4/4/11440/11440-8.txt, A Shop In Go-By Street