Man can learn nothing unless he proceeds from the known to the unknown.
Experimentation is an active science.
Science does not permit exceptions.
Science repulses the indefinite.
True science teaches us to doubt and to abstain from ignorance.
The investigator should have a robust faith - and yet not believe.
They 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.
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.