To be wiser than other men is to be honester than they; and strength of mind is only courage to see and speak the truth.

There is a heroism in crime as well as in virtue. Vice and infamy have their altars and their religion.

The origin of all science is the desire to know causes, and the origin of all false science is the desire to accept false causes rather than none; or, which is the same thing, in the unwillingness to acknowledge our own ignorance.

Shall I faint, now that I have poured out the spirit of my mind to the world, and treated many subjects with truth, with freedom, with power, because I have been followed with one cry of abuse ever since for not being a Government tool?

There is a secret pride in every human heart that revolts at tyranny. You may order and drive an individual, but you cannot make him respect you.

Pure good soon grows insipid, wants variety and spirit. Pain is a bittersweet, which never surfeits. Love turns, with a little indulgence, to indifference or disgust. Hatred alone is immortal.

Do not keep on with a mockery of friendship after the substance is gone - but part, while you can part friends. Bury the carcass of friendship: it is not worth embalming.