A fact in itself is nothing. It is valuable only for the idea attached to it, or for the proof which it furnishes.

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

Il ne fallait jamais faire des expériences pour confirmer ses idées, mais simplement pour les contrôler. We must never make experiments to confirm our ideas, but simply to control them.