In a living civilization there is always an element of unrest, for sensitiveness to ideas means curiosity, adventure, change. Civilized order survives on its merits and is transformed by its power of recognizing its imperfections.

The pursuit of mathematics is a divine madness of the human spirit.

What is morality in any given time or place? It is what the majority then and there happen to like and immorality is what they dislike.

In order to acquire learning, we must first shake ourselves free of it.

The ideas of Freud were popularized by people who only imperfectly understood them, who were incapable of the great effort required to grasp them in their relationship to larger truths, and who therefore assigned to them a prominence out of all proportion to their true importance.

Without adventure civilization is in full decay.

It belongs to the self-respect of intellect to pursue every tangle of thought to its final unravelment.