Having with as much brevity as just suffices for that purpose, explained the nature of the principle in question, and its use by society at large, it now only remains that I should explain that purpose itself, by theory and example.
What I am doing in tracing the unanimity principle from its first instinctive use by the public to its secondary and meditated one by philosophy, is a purely critical act, comparable to that of the rhetorician who appreciates the character of certain modes of thinking which have long since been practised by mankind, and shows what therein is approvable--all the rest being liable to censure.
It was the universal conviction of European Christendom, during many centuries, that the Church, which was popularly supposed to be represented by the Pope, enjoyed peculiarly a divine guidance which made it an infallible judge of truth. This idea was thought to be warranted by the unanimous assent of all right-minded persons, and the denial of it to be the mark of a reprobate spirit, as well as contrary to common sense. We now know the entire futility of this assumption, and that the heretics were not inferior to the orthodox in the power of judging such subjects. Hence in discussing the unanimity principle the question presents itself, How came the public thus wrongly to apply it? What error did they commit in so doing? When the revival of learning and the consequent rise of Protestantism had exposed the error in that form of it, it was still continued under the new social regimes; so that even Locke, the boldest advocate of the rights of man that was tolerated even in his time, stigmatised the dissentients from certain Protestant tenets in the same unjust way that Popery had done to the dissentients from certain Popish ones; speaking of them in two or three places of his essay as persons at once notoriously disreputable in character and weak in intellect; consistently with which estimate he came to the conclusion that the reigning theology was established truth, as being accredited by all those whose opinion was worth taking account of.
Later times have again manifested the futility of the assumption against the new race of dissentients. No one will say that Goethe and Neibuhr (to mention only two) must count for nothing on questions wherein they were as likely to be well informed as their opponents. So that Locke's side, instead of being warranted by the decisive verdict he imagines, is but one of two suitors in an undetermined cause, neither having yet attracted the votes of the whole jury, and neither consequently yet occupying the position of ascertained truth. Giving everyone a fair hearing is that trial and test of competency which yields the only means of learning who said competent judges are.