"Power acquired by violence is only a usurpation, and lasts only as long as the force of him who commands prevails over that of those who obey."

"No man has received from nature the right to command his fellow human beings."

"When superstition is allowed to perform the task of old age in dulling the human temperament, we can say goodbye to all excellence in poetry, in painting, and in music."

"When science, art, literature, and philosophy are simply the manifestation of personality they are on a level where glorious and dazzling achievements are possible, which can make a man's name live for thousands of years."

"One thorn of experience is worth a whole wilderness of warning."

"There is no subject on which more dangerous nonsense is talked and thought than marriage."

"By indignities men come to dignities."

"It is one of the blessings of old friends that you can afford to be stupid with them."