Everything we hear is an opinion, not a fact. Everything we see is a perspective, not the truth.
-- Marcus Aurelius
It's no wonder that truth is stranger than fiction. Fiction has to make sense.
-- Mark Twain
"I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use."
-- Galileo Galilei
My personal favorite is not really a one line but it is held together by semi colons. Its from Daniel Webster:
A good one that makes a lot of sense. Its a waste of time to think about what others opinion could be of me: