Mysterious in the light of day, nature retains her veil, despite our clamours: That which she does not willingly display cannot be wrenched from her with levers, screws and hammers.

How can we know ourselves? Never by reflection, but only through action. Begin at once to do your duty and immediately you will know what is inside you.

He who possesses art and science has religion; he who does not possess them, needs religion.

There are situations in which hope and fear run together, in which they mutually destroy one another and lose themselves in dull indifference.

The world is so empty if one thinks only of mountains, rivers and cities; but to know someone who thinks and feels with us, and who, though distant, is close to us in spirit, this makes the earth for us an inhabited garden.

The greatest thing in this world is not so much where we stand as in what direction we are moving.

Hypotheses are the scaffolds which are erected in front of a building and removedd when the building is completed. They are indispensable to the worker; but the worker must not mistake the scaffolding for the building.