The continuing zombie discussion has reminded me of Raymond Smullyan, and conveniently someone has posted the essay I wanted from This Book Needs No Title: "The Unfortunate Dualist." A shorter piece, "Is Man a Machine?" connects this topic to Joy in the Merely Real. Essential paragraph:

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!"