"Theories are only verified hypotheses, verified by more or less numerous facts. Those verified by the most facts are the best, but even then they are never final, never to be absolutely believed."

“A modern poet has characterized the personality of art and the impersonality of science as follows: Art is I: Science is We.”

“A great surgeon performs operations for stone by a single method; later he makes a statistical summary of deaths and recoveries, and he concludes from these statistics that the mortality law for this operation is two out of five. Well, I say that this ratio means literally nothing scientifically and gives us no certainty in performing the next operation; for we do not know whether the next case will be among the recoveries or the deaths. What really should be done, instead of gathering facts empirically, is to study them more accurately, each in its special determinism….to discover in them the cause of mortal accidents so as to master the cause and avoid the accidents.”

“Indeed, proof that a given condition always precedes or accompanies a phenomenon does not warrant concluding with certainty that a given condition is the immediate cause of that phenomenon. It must still be established that when this condition is removed, the phenomen will no longer appear.”

“We must never make experiments to confirm our ideas, but simply to control them.”

“The stability of the internal medium is a primary condition for the freedom and independence of certain living bodies in relation to the environment surrounding them.”

“If I had to define life in a word, it would be: Life is creation.”