Algebra reverses the relative importance of the factors in ordinary language.

The deepest definition of youth is life as yet untouched by tragedy.

Every philosophy is tinged with the coloring of some secret imaginative background, which never emerges explicitly into its train of reasoning.

There are no whole truths: all truths are half-truths. It is trying to treat them as whole truths that plays to the devil.

A philosopher of imposing stature doesn't think in a vacuum. Even his most abstract ideas are, to some extent, conditioned by what is or is not known in the time when he lives.

To come very near to a true theory, and to grasp its precise application, are two different things, as the history of science teaches us. Everything of importance has been said before by someone who did not discover it.

From the very beginning of his education, the child should experience the joy of discovery.