One can know nothing of giving aught that is worthy to give unless one also knows how to take.

The conflict of forces and the struggle of opposing wills are of the essence of our universe and alone hold it together.

The mathematician has reached the highest rung on the ladder of human thought.

It is on our failures that we base a new and different and better success.

Beauty is the child of love.

Here, where we reach the sphere of mathematics, we are among processes which seem to some the most inhuman of all human activities and the most remote from poetry. Yet it is here that the artist has the fullest scope of his imagination.

The by-product is sometimes more valuable than the product.