"It's one thing to not want an evil-sorcerer type villain in your story, but it's another thing to avoid having any sort of antagonist at all. A story without an antagonist gets weird pretty quick."

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So my antagonist said, "Is it impossible that there are flying saucers? Can you prove that it's impossible?" "No," I said, "I can't prove it's impossible. It's just very unlikely." At that he said, "You are very unscientific. If you can't prove it impossible then how can you say that it's unlikely?" But that is the way that is scientific. It is scientific only to say what is more likely and what less likely, and not to be proving all the time the possible and impossible.

— Richard P. Feynman