It often happens that the universal belief of one age of mankind — a belief from which no one was, nor without an extraordinary effort of genius and courage, could at that time be free — becomes to a subsequent age so palpable an absurdity, that the only difficulty then is to imagine how such a thing can ever have appeared credible.

The true virtue of human beings is fitness to live together as equals; claiming nothing for themselves but what they as freely concede to everyone else; regarding command of any kind as an exceptional neccessity, and in all cases a temporary one.

... All ideas need to be heard, because each idea contains one aspect of the truth. By examining that aspect, we add to our own idea of the truth. Even ideas that have no truth in them whatsoever are useful because by disproving them, we add support to our own ideas.

So long as an opinion is strongly rooted in the feelings, it gains rather than loses in stability by having a preponderating weight of argument against it.

Every established fact which is too bad to admit of any other defence is always presented to us as an injunction of religion.

Of two pleasures, if there be one which all or almost all who have experience of both give a decided preference, irrespective of any feeling of moral obligation to prefer it, that is the more desirable pleasure.

Every great movement must experience three stages: ridicule, discussion, adoption.