No man of science wants merely to know. He acquires knowledge to appease his passion for discovery. He does not discover in order to know, he knows in order to discover.

Everyone is a philosopher. Not everyone is good at it.

The importance of an individual thinker owes something to chance. For it depends upon the fate of his ideas in the minds of his successors.

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

The study of mathematics is apt to commence in disappointment... We are told that by its aid the stars are weighed and the billions of molecules in a drop of water are counted. Yet, like the ghost of Hamlet's father, this great science eludes the efforts of our mental weapons to grasp it.

It is more important that a proposition be interesting than that it be true.

I have suffered a great deal from writers who have quoted this or that sentence of mine either out of its context or in juxtaposition to some incongruous matter which quite distorted my meaning, or destroyed it altogether.