If you think you understand quantum mechanics, you don't understand quantum mechanics.
Richard P. FeynmanThe whole question of imagination in science is often misunderstood by people in other disciplines. ... They overlook the fact that whatever we are allowed to imagine in science must be consistent with everything else we know.
Richard P. FeynmanTo test whether you have learned an idea or a definition, rephrase what you just learned without using the new word.
Richard P. FeynmanFirst you guess. Don't laugh, this is the most important step. Then you compute the consequences. Compare the consequences to experience. If it disagrees with experience, the guess is wrong. In that simple statement is the key to science. It doesn't matter how beautiful your guess is or how smart you are or what your name is. If it disagrees with experience, it's wrong. That's all there is to it.
Richard P. Feynman