The ultimate court of appeal is observation and experiment... not authority.

Learn what is true in order to do what is right.

No slavery can be abolished without a double emancipation, and the master will benefit by freedom more than the freed-man.

Not only does every animal live at the expense of some other animal or plant, but the very plants are at war.... The individuals of a species are like the crew of a foundered ship, and none but good swimmers have a chance of reaching the land.

To a clear eye the smallest fact is a window through which the infinite may be seen.

If a man cannot see a church, it is preposterous to take his opinion about its altar-piece or painted window.

Every living creature commences its existence under a form different from, and simpler than, that which it eventually attains.