The Unicorn looked dreamily at Alice, and said “Talk,
child.”

Alice could not help her lips curling up into a smile as
she began: “Do you know, I always thought Unicorns were fabulous monsters, too?
I never saw one alive before!”

“Well, now that we have seen each other,” said the
Unicorn, “if you’ll believe in me, I’ll believe in you. Is that a bargain?” 

–Lewis Carroll, Through the
Looking-Glass, ch. VII, 1872