Our ideas are only intellectual instruments which we use to break into phenomena; we must change them when they have served their purpose, as we change a blunt lancet that we have used long enough.
The mental never influences the physical. It is always the physical that modifies the mental, and when we think that the mind is diseased, it is always an illusion.
Those who have an excessive faith in their theories or in their ideas are not only poorly disposed to make discoveries, but they also make very poor observations.
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.
The better educated we are and the more acquired information we have, the better prepared shall we find our minds for making great and fruitful discoveries.
