First causes are outside the realm of science.
Now, a living organism is nothing but a wonderful machine endowed with the most marvellous properties and set going by means of the most complex and delicate mechanism.
In the philosophic sense, observation shows and experiment teaches.
The joy of discovery is certainly the liveliest that the mind of man can ever feel.
The science of life is a superb and dazzlingly lighted hall which may be reached only by passing through a long and ghastly kitchen.
Feeling alone guides the mind.
The fact that knowledge endlessly recedes as the investigator is about to grasp it is what constitutes at the same time his torment and happiness.
Effects vary with the conditions which bring them to pass, but laws do not vary. Physiological and pathological states are ruled by the same forces; they differ only because of the special conditions under which the vital laws manifest themselves.
Tout est poison, rien n’est poison, tout est une question de dose. Everything is poisonous, nothing is poisonous, it is all a matter of dose.
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.
We must remain, in a word, in an intellectual disposition which seems paradoxical, but which, in my opinion, represents the true mind of the investigator. We must have a robust faith and yet not believe.
Mediocre men often have the most acquired knowledge.
The great experimental principle, then, is doubt, that philosophic doubt which leaves to the mind its freedom and initiative, and from which the virtues most valuable to investigators in physiology and medicine are derived.
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.
Experiment is fundamentally only induced observation.
A man of science rises ever, in seeking truth; and if he never finds it in its wholeness, he discovers nevertheless very significant fragments; and these fragments of universal truth are precisely what constitutes science.
A discovery is generally an unforeseen relation not included in theory.
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.
Particular facts are never scientific; only generalization can establish science.
Obervation is a passive science, experimentation is an active science.
We must never make experiments to confirm our ideas, but simply to control them.