If a dog jumps into your lap, it is because he is fond of you; but if a cat does the same thing, it is because your lap is warmer.

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 impossible to meditate on time and the mystery of nature without an overwhelming emotion at the limitations of human intelligence.

The great achievements of the past were the adventures of the past. Only the adventurous can understand the greatness of the past.

I put forward as a general definition of civilization, that a civilized society is exhibiting the five qualities of Truth, Beauty, Adventure, Art, Peace.

The point about zero is that we do not need to use it in the operation of daily life. No one goes out to buy zero fish.

The true method of discovery is like the flight of an aeroplane. It starts from the ground of particular observation; it makes a flight in the thin air of imaginative generalization; and it again lands for renewed observation rendered acute by rational interpretation.