Carl Sagan on being challenged to engage in critical self-examination

All of us cherish our beliefs. They are, to a degree, self-defining. When someone comes along who challenges our belief system as insufficiently well-based -- or who, like Socrates, merely asks embarrassing questions that we haven't thought of, or demonstrates that we've swept key underlying assumptions under the rug -- it becomes much more than a search for knowledge. It feels like a personal assault.

--Carl Sagan, The Demon-Haunted World