I imagine that if my friend finally came to the conclusion that he were a machine, he would be infinitely crestfallen. I think he would think: "My God! How Horrible! I am only a machine!" But if I should find out I were a machine, my attitude would be totally different. I would say: "How amazing! I never before realized that machines could be so marvelous!"

(Raymond Smullyan)

I have found it in an OB comment by Zubon, but it was never posted as a rationality quote.