As we advance in life, we learn the limits of our abilities.
Every one of us ... knows better than he practices, and recognizes a better law than he obeys.
Science rests on reason and experiment, and can meet an opponent with calmness; [but] a creed is always sensitive.
To be happy is not the purpose for which you are placed in this world.
Fear is the parent of cruelty.
To deny the freedom of the will is to make morality impossible.