"The one who contributed most to break down the barrier between physical method and metaphysical method, and to confound their domains, so clearly distinguished in the Aristotelian philosophy, was surely Descartes."

“A physical theory reputed to be satisfactory by the sectarians of one metaphysical school will be rejected by the partisans of another school.”

“Agreement with experiment is the sole criteria of truth for a physical theory.”

“Every time people cite a principle of theoretical physics in support of a metaphysical doctrine or physical dogma, they commit a mistake, for they attribute to this principle a meaning not its own, an import not belonging to it.”

“There you have, then, a theoretical physics which is neither the theory of a believer nor that of a nonbeliever, but merely and simply a theory of a physicist; admirably suited to classify the laws studied by the experimenter, it is incapable of opposing any assertion whatever of metaphysics or of religious dogma, and is equally incapable of lending effective support to any such assertion.”