Unless a thing can be defined ...

Unless a thing can be defined by measurement, it has no place in a theory. And since an accurate value of the momentum of a localized particle cannot be defined by measurement it therefore has no place in the theory.
Unless a thing can be defined by measurement, it has no place in a theory. And since an accurate value of the momentum of a localized particle cannot be defined by measurement it therefore has no place in the theory.
 Richard P. Feynman

More phrases

Courage - a perfect sensibility of the measure of danger, and a mental willingness to endure it.
 William Tecumseh Sherman
I'm pretty conservative when it comes to money. My parents were very working class and constantly working. There was always a very strong work ethic and that's put a more conservative, "save for a rainy day" mentality into me.
The kind of group mentality that we had lived under since the Second World War is starting to erupt, and the craving for individualism is now much stronger. It's not as taboo anymore, as it was when I was younger.
 Nicolas Winding Refn
The overall similarity is probably in the mentality of law enforcement officers. There's a sense of wanting to really uphold a sense of morality and make sure that the laws are enforced to the letter, whenever possible.
 Benjamin McKenzie
Courage is rightly esteemed the first of human qualities... because it is the quality which guarantees all others.

Quotes from the same author

From a long view of the history of mankind, seen from, say, ten thousand years from now, there can be little doubt that the most significant event of the 19th century will be judged as Maxwell's discovery of the laws of electrodynamics. The American Civil War will pale into provincial insignificance in comparison with this important scientific event of the same decade.
 Richard P. Feynman
My friends and I had taken dancing lessons, although none of us would ever admit it. In those depression days, a friend of my mother was trying to make a living by teaching dancing in the evening, in an upstairs dance studio. There was a back door to the place, and she arranged it so the young men could come up through the back way without being seen.
 Richard P. Feynman
If science is to progress, what we need is the ability to experiment, honesty in reporting results—the results must be reported without somebody saying what they would like the results to have been—and finally—an important thing—the intelligence to interpret the results.
 Richard P. Feynman
The only way to deep happiness is to do something you love to the best of your ability
 Richard P. Feynman
To do any important work in physics a very good mathematical ability and aptitude are required. Some work in applications can be done without this, but it will not be very inspired. If you must satisfy your "personal curiosity concerning the mysteries of nature" what will happen if these mysteries turn out to be laws expressed in mathematical terms (as they do turn out to be)? You cannot understand the physical world in any deep or satisfying way without using mathematical reasoning with facility.
 Richard P. Feynman