Tolerance too is learned in discussion, and, as history shows, is only so learned. In all customary societies bigotry is the ruling principle. In rude places to this day any one who says anything new is looked on with suspicion, and is persecuted by opinion if not injured by penalty. One of the greatest pains to human nature is the pain of a new idea. It is, as common people say, so 'upsetting;' it makes you think that, after all, your favourite notions may be wrong, your firmest beliefs ill-founded; it is certain that till now there was no place allotted in your mind to the new and startling inhabitant, and now that it has conquered an entrance you do not at once see which of your old ideas it will or will not turn out, with which of them it can be reconciled, and with which it is at essential enmity. Naturally, therefore, common men hate a new idea, and are disposed more or less to ill-treat the original man who brings it. Even nations with long habits of discussion are intolerant enough. In England, where there is on the whole probably a freer discussion of a greater number of subjects than ever was before in the world, we know how much power bigotry retains. But discussion, to be successful, requires tolerance. It fails wherever, as in a French political assembly, any one who hears anything which he dislikes tries to howl it down. If we know that a nation is capable of enduring continuous discussion, we know that it is capable of practising with equanimity continuous tolerance.