In teaching man, experimental science results in lessening his pride more and more by proving to him every day that primary causes, like the objective reality of things, will be hidden from him forever and that he can only know relations.

The doubter is a true man of science: he doubts only himself and his interpretations, but he believes in science.

The experimenter who does not know what he is looking for will not understand what he finds.

Obervation is a passive science, experimentation is an active science.

Men who have excessive faith in their theories ... make poor observations, because they choose among the results of their experiments only what suits their object, neglecting whatever is unrelated to it and carefully setting aside everything which might tend toward the idea they wish to combat

The goal of scientific physicians in their own science ... is to reduce the indeterminate. Statistics therefore apply only to cases in which the cause of the facts observed is still indeterminate.

A fact in itself is nothing. It is valuable only for the idea attached to it, or for the proof which it furnishes.