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.

Obervation is a passive science, experimentation is an active science.

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

True science teaches us to doubt and, in ignorance, to refrain.

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

It is impossible to devise an experiment without a preconceived idea; devising an experiment, we said, is putting a question; we never conceive a question without an idea which invites an answer. I consider it, therefore, an absolute principle that experiments must always be devised in view of a preconceived idea, no matter if the idea be not very clear nor very well defined.

Laplace considers astronomy a science of observation, because we can only observe the movements of the planets; we cannot reach them, indeed, to alter their course and to experiment with them. "On earth," said Laplace, "we make phenomena vary by experiments; in the sky, we carefully define all the phenomena presented to us by celestial motion." Certain physicians call medicine a science of observations, because they wrongly think that experimentation is inapplicable to it.