Maier's Law:
If the facts don't conform to the theory, they must be disposed of.
Corollaries:
(1) The bigger the theory, the better.
(2) The experiment may be considered a success if no more than 50% of the observed measurements must be discarded to obtain a correspondence with the theory.
If today is the first day of the rest of your life, what the hell was yesterday?
We are all agreed that your theory is crazy. The question which divides us is whether it is crazy enough to have a chance of being correct. My own feeling is that it is not crazy enough.
— Niels Bohr
By the way, many of the quotes are from the unix fortune file (heavily culled to only include my absolute favorites). Some are from Usenet, some are from email, and other are simply from the real world.