Unfortunately for the good sense of mankind, the fact of their fallibility is far from carrying the weight in their practical judgment which is always allowed to it in theory; for while every one well knows himself to be fallible, few think it necessary to take any precautions against their own fallibility, or admit the supposition that any opinion, of which they feel very certain, may be one of the examples of the error to which they acknowledge themselves to be liable. Absolute princes, or others who are accustomed to unlimited deference, usually feel this complete confidence in their own opinions on nearly all subjects. People more happily situated, who sometimes hear their opinions disputed, and are not wholly unused to be set right when they are wrong, place the same unbounded reliance only on such of their opinions as are shared by all who surround them, or to whom they habitually defer; for in proportion to a man's want of confidence in his own solitary judgment, does he usually repose, with implicit trust, on the infallibility of "the world" in general. And the world, to each individual, means the part of it with which he comes in contact; his party, his sect, his church, his class of society; the man may be called, by comparison, almost liberal and large-minded to whom it means anything so comprehensive as his own country or his own age. Nor is his faith in this collective authority at all shaken by his being aware that other ages, countries, sects, churches, classes, and parties have thought, and even now think, the exact reverse. He devolves upon his own world the responsibility of being in the right against the dissentient worlds of other people; and it never troubles him that mere accident has decided which of these numerous worlds is the object of his reliance, and that the same causes which make him a Churchman in London, would have made him a Buddhist or a Confucian in Pekin. Yet it is as evident in itself, as any amount of argument can make it, that ages are no more infallible than individuals; every age having held many opinions which subsequent ages have deemed not only false but absurd; and it is as certain that many opinions now general will be rejected by future ages, as it is that many, once general, are rejected by the present.
The objection likely to be made to this argument would probably take some such form as the following. There is no greater assumption of infallibility in forbidding the propagation of error, than in any other thing which is done by public authority on its own judgment and responsibility. Judgment is given to men that they may use it.
Because it may be used erroneously, are men to be told that they ought not to use it at all? To prohibit what they think pernicious, is not claiming exemption from error, but fulfilling the duty incumbent on them, although fallible, of acting on their conscientious conviction. If we were never to act on our opinions, because those opinions may be wrong, we should leave all our interests uncared for, and all our duties unperformed. An objection which applies to all conduct can be no valid objection to any conduct in particular. It is the duty of governments, and of individuals, to form the truest opinions they can; to form them carefully, and never impose them upon others unless they are quite sure of being right. But when they are sure (such reasoners may say), it is not conscientiousness but cowardice to shrink from acting on their opinions, and allow doctrines which they honestly think dangerous to the welfare of mankind, either in this life or in another, to be scattered abroad without restraint, because other people, in less enlightened times, have persecuted opinions now believed to be true. Let us take care, it may be said, not to make the same mistake: but governments and nations have made mistakes in other things, which are not denied to be fit subjects for the exercise of authority: they have laid on bad taxes, made unjust wars. Ought we therefore to lay on no taxes, and, under whatever provocation, make no wars? Men, and governments, must act to the best of their ability. There is no such thing as absolute certainty, but there is assurance sufficient for the purposes of human life. We may, and must, assume our opinion to be true for the guidance of our own conduct: and it is assuming no more when we forbid bad men to pervert society by the propagation of opinions which we regard as false and pernicious.
I answer, that it is assuming very much more. There is the greatest difference between presuming an opinion to be true, because, with every opportunity for contesting it, it has not been refuted, and assuming its truth for the purpose of not permitting its refutation. Complete liberty of contradicting and disproving our opinion is the very condition which justifies us in assuming its truth for purposes of action; and on no other terms can a being with human faculties have any rational assurance of being right.