Ignorance is the worst form of slavery. (Paraphrased)

Commerce is the great civilizer.

To be like other people is to be unlike ourselves.

If abuses are destroyed, man must destroy them. If slaves are freed, man must free them. If new truths are discovered, man must discover them. If the naked are clothed; if the hungry are fed; if justice is done; if labor is rewarded; if superstition is driven from the mind; if the defenseless are protected, and if the right finally triumphs, all must be the work of man. The grand victories of the future must be won by man, and by man alone.

Either god should have written a book to fit my brain, or he should have made my brain to fit his book.

Tell me there is a God in the serene heavens that will damn his children for the expression of an honest belief! More men have died in their sins, judged by your orthodox creeds, than there are leaves in all the forests in the wide world ten thousand times over. Tell me these men are in Hell; that these men are in torment; that these children are in eternal pain, and that they are to be punished forever and forever! I denounce this doctrine as the most infamous of lies.

[T]he blossom of benevolence, of charity, is the fairest flower, no matter whether it blooms by the side of a hovel, or bursts from a vine climbing the marble pillar of a palace. I respect no man because he is rich; I hold in contempt no man because he is poor.