"We absolutely must leave room for doubt or there is no progress and there is no learning. There is no learning without having to pose a question. And a question requires doubt. People search for certainty. But there is no certainty. People are terrified â€” how can you live and not know? It is not odd at all. You only think you know, as a matter of fact. And most of your actions are based on incomplete knowledge and you really donâ€™t know what it is all about, or what the purpose of the world is, or know a great deal of other things. It is possible to live and not know."

Source : "The Pleasure of Finding Things Out". Book by Richard P. Feynman, 1999.

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