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The first principle is that you must not fool yourself — and you are the easiest person to fool.

— Richard Feynman

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Source: "Cargo Cult Science", adapted from a 1974 Caltech commencement address; also published in Surely You're Joking, Mr. Feynman!, p. 343
Source quality: Precise citation Points to a specific work with a page, chapter, date or similar locator, so you can look it up.

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Scientific knowledge is an enabling power to do either good or bad — but it does not carry instructions on how to use it.

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Science is the belief in the ignorance of experts.

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It is not unscientific to make a guess, although many people who are not in science think it is.

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You can recognize truth by its beauty and simplicity.

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I don't know anything, but I do know that everything is interesting if you go into it deeply enough.

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I learned very early the difference between knowing the name of something and knowing something.

What Do You Care What Other People Think? (1988)

Hell, if I could explain it to the average person, it wouldn't have been worth the Nobel prize.

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Tell your son to stop trying to fill your head with science — for to fill your heart with love is enough!

For a successful technology, reality must take precedence over public relations, for nature cannot be fooled.

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Attribution

Quote text and notes from Wikiquote: Richard Feynman (page history), available under CC BY-SA 4.0. Source quality and labels are our own summary of what Wikiquote records.