"Anyone who would attempt the task of felling a virgin forest with a penknife would probably feel the same paralysis of despair that the reformer feels when confronted with existing school systems."

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We cannot define anything precisely. If we attempt to, we get into the paralysis of thought that comes to philosophers, who sit opposite each other, one saying to the other, "You don't know what you are talking about!" The second one says, "What do you mean by know? What do you mean by talking? What do you mean by you?"

— Richard P. Feynman