The initial quote I had in mind was:
“I would rather have questions that can’t be answered than answers that can’t be questioned.” — Richard P. Feynman
But, as @Vectorman points out, Feynman has lots of good quotes. One of my other favorites is:
“The first principle is that you must not fool yourself, and you are the easiest person to fool.”
One of the best descriptions of how “science is done” is in his reply in a Q&A session:
“In general, we look for a new law by the following process. First, we guess it (audience laughter), no, don’t laugh, that’s really true. Then we compute the consequences of the guess, to see what, if this is right, if this law we guess is right, to see what it would imply and then we compare the computation results to nature, or we say compare to experiment or experience, compare it directly with observations to see if it works.
“If it disagrees with experiment, it’s wrong. In that simple statement is the key to science. It doesn’t make any difference how beautiful your guess is, it doesn’t matter how smart you are who made the guess, or what his name is.… If it disagrees with experiment, it’s wrong. That’s all there is to it.”
All of this makes me wish Feynman were still alive and able to debate some of the “Man-Made Climate Change” Warriors.