"Two seemingly incompatible conceptions can each represent an aspect of the truth … They may serve in turn to represent the facts without ever entering into direct conflict."

“The actual state of our knowledge is always provisional and … there must be, beyond what is actually known, immense new regions to discover.”

“The history of science shows that the progress of science has constantly been hampered by the tyrannical influence of certain conceptions that finally came to be considered as dogma. For this reason, it is proper to submit periodically to a very searching examination, principles that we have come to assume without any more discussion.”

“It seems a little paradoxical to construct a configuration space with the coordinates of points which do not exist.”