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 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