My business is to teach my aspirations to confirm themselves to fact, not to try and make facts harmonize with my aspirations.

Do what you can to do what you ought, and leave hoping and fearing alone.

A good man: body serves his will and enjoys hard work, clear intellect that understands the truths of nature, full of passion for life but controlled by his will, well-developed conscience, loves beauty in art and nature, despises inferior morality, respects himself and others.

Life is too short to occupy oneself with the slaying of the slain more than once.

Extinguished theologians lie about the cradle of every science, as strangled snakes beside that of Hercules

Skepticism is the highest duty and blind faith the one unpardonable sin.

Of moral purpose I see no trace in Nature. That is an article of exclusively human manufacture and very much to our credit.