Mathematics has the completely false reputation of yielding infallible conclusions. Its infallibility is nothing but identity. Two times two is not four, but it is just two times two, and that is what we call four for short. But four is nothing new at all. And thus it goes on and on in its conclusions, except that in the higher formulas the identity fades out of sight.

This is the highest wisdom that I own; freedom and life are earned by those alone who conquer them each day anew.

At the end of life thoughts hitherto impossible come to the collected mind, like good spirits which let themselves down from the shining heights of the past.

Of the book of books most wondrous is the tender book of love.

Always to distrust is an error, as well as always to trust.

Mankind? That is an abstraction. There have always been and always will be only individuals.

The most difficult thing is what is thought to be the simplest; to really see the things which are before your eyes.