The only freedom which deserves the name is that of pursuing our own good, in our own way, so long as we do not attempt to deprive others of theirs, or impede their efforts to obtain it.
Human nature is not a machine to be built after a model, and set to do exactly the work prescribed for it, but a tree, which requires to grow and develop itself on all sides, according to the tendency of the inward forces which make it a living thing.
All political revolutions, not affected by foreign conquest, originate in moral revolutions. The subversion of established institutions is merely one consequence of the previous subversion of established opinions.
To refuse a hearing to an opinion, because they are sure that it is false, is to assume that their certainty is the same thing as absolute certainty. All silencing of discussion is an assumption of infallibility.
Truth gains more even by the errors of one who, with due study and preparation, thinks for himself, than by the true opinions of those who only hold them because they do not suffer themselves to think.
War is an ugly thing, but not the ugliest of things. The decayed and degraded state of moral and patriotic feeling which thinks that nothing is worth war is much worse.
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.
