When one's ideas are not challenged, one's ability to defend them weakens.

Next to selfishness the principal cause which makes life unsatisfactory is want of mental cultivation.

All silencing of discussion is an assumption of infallibility.

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.

Mankind are greater gainers by suffering each other to live as seems good to themselves, than by compelling each to live as seems good to the rest.

To do as one would be done by, and to love one's neighbour as oneself, constitute the ideal perfection of utilitarian morality

There is always need of persons not only to discover new truths, and point out when what were once truths are true no longer, but also to commence new practices, and set the example of more enlightened conduct, and better taste and sense in human life.