Theories are like a stairway; by climbing, science widens its horizon more and more, because theories embody and necessarily include proportionately more facts as they advance.

Real science exists, then, only from the moment when a phenomenon is accurately defined as to its nature and rigorously determined in relation to its material conditions, that is, when its law is known. Before that, we have only groping and empiricism.

Well-observed facts, though brought to light by passing theories, will never die; they are the material on which alone the house of science will at last be built.

The joy of discovery is certainly the liveliest that the mind of man can ever feel.

In a word, I consider hospitals only as the entrance to scientific medicine; they are the first field of observation which a physician enters; but the true sanctuary of medical science is a laboratory; only there can he seek explanations of life in the normal and pathological states by means of experimental analysis.

Men who believe too firmly in their theories, do not believe enough in the theories of others. So ... these despisers of their fellows ... make experiments only to destroy a theory, instead of to seek the truth.

Art is 'I'; science is 'we'.