"I knew,"wrote Claude Bernard, "the scientist's pain who, by absence of supports, cannot carry out the experiments that he conceives, and who is forced to abandon certain researches, or to leave his discovery in a state of an outset."
The constancy of the internal environment is the condition that life should be free and independent.... So far from the higher animal being indifferent to the external world, it is on the contrary in a precise and informed relation with it, in such a way that its equilibrium results from a continuous and delicate compensation, established as by the most sensitive of balances
A fact in itself is nothing, it is valuable only for the ideas attached to it, or for the proof which it furnishes.
it is what we think we know already that prevent us from learning.
...we must of necessity go down to objective reality..... In the search for truth by the experimental method, feeling always takes the lead: it begets the a priori idea or intuition: reasoning develops the idea and deduces its logical consequences. But if feeling must be clarified by reason, reason must in turn be guided by experiment.
