One has to do something new in order to see something new.

Perhaps pure reason without heart would never have thought of God.

The natural scientists of the previous age knew less than we do and believed they were very close to the goal: we have taken very great steps in its direction and now discover we are still very far away from it. With the most rational philosophers an increase in their knowledge is always attended by an increased conviction of their ignorance.

When an acquaintance goes by I often step back from my window, not so much to spare him the effort of acknowledging me as to spare myself the embarrassment of seeing that he has not done so.

When a book and a head collide and a hollow sound is heard, must it always have come from the book?

Just as we outgrow a pair of trousers, we outgrow acquaintances, libraries, principles, etc., at times before they're worn out and times - and this is the worst of all - before we have new ones.

We now possess four principles of morality: 1) a philosophical: do good for its own sake, out of respect for the law; 2) a religious: do good because it is God's will, out of love of God; 3) a human: do good because it will promote your happiness, out of self-love; 4) a political: do good because it will promote the welfare of the society of which you are a part, out of love of society having regard to yourself. But is this not all one single principle, only viewed from different sides?