" The expression 'self-evident' means properly that the proposition so called is evident or true, by itself alone; that it is not an inference from some proposition other than itself. The expression does not mean that the proposition is true, because it is evident to you or me or all mankind, because in other words in appears to us to be true. That a proposition appears to be true can never be a valid argument that true it really is. "

― George Edward Moore , Principia Ethica (Philosophical Classics)