[238] between assuming 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.
(2) If the received opinion which it is sought to protect against the intrusion of error is true, the suppression of discussion is still contrary to general utility. A received opinion may happen to be true (it is very seldom entirely true); but a rational certainty that it is so can only be secured by the fact that it has been fully canvassed but has not been shaken.
Commoner and more important is (3) the case where the conflicting doctrines share the truth between them. Here Mill has little difficulty in proving the utility of supplementing one-sided popular truths by other truths which popular opinion omits to consider. And he observes that if either of the opinions which share the truth has a claim not merely to be tolerated but to be encouraged, it is the one which happens to be held by the minority, since this is the one which
[239] for the time being represents the neglected interests. He takes the doctrines of Rousseau, which might conceivably have been suppressed as pernicious. To the self-complacent eighteenth century those doctrines came as a salutary shock, dislocating the compact mass of one-sided opinion. The current opinions were indeed nearer to the truth than Rousseaus, they contained much less of error; nevertheless there lay in Rousseaus doctrine, and has floated down the stream of opinion along with it, a considerable amount of exactly those truths which the popular opinion wanted; and these are the deposit which we left behind when the flood subsided.
Such is the drift of Mills main argument. The present writer would prefer to state the justification of freedom of opinion in a somewhat different form, though in accordance with Mills reasoning. The progress of civilization, if it is partly conditioned by circumstances beyond mans control, depends more, and in an increasing measure, on things which are within his own power. Prominent among these are the advancement of knowledge and the deliberate adaptation of his habits and institutions to new conditions. To advance knowledge and to correct errors, unrestricted freedom of discussion is required.