"If then it be possible that one contrary should exist, or be called into existence, the other contrary will also appear to be possible."

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On the contrary, it's because somebody knows something about it that we can't talk about physics . It's the things that nobody knows anything about that we can discuss. We can talk about the weather; we can talk about social problems; we can talk about psychology; we can talk about international finance gold transfers we can't talk about, because those are understood so it's the subject that nobody knows anything about that we can all talk about!

— Richard P. Feynman