The worthwhile problems are the ones you can really solve or help solve, the ones you can really contribute something to... No problem is too small or too trivial if we can really do something about it.
Richard P. FeynmanHave no respect whatsoever for authority; forget who said it and instead look what he starts with, where he ends up, and ask yourself, "Is it reasonable?"
Richard P. FeynmanSome things that satisfy the rules of algebra can be interesting to mathematicians even though they don't always represent a real situation.
Richard P. Feynman