For no one really ceases to be a revolutionary Communist or a passionate Roman Catholic by being forbidden to be either of these. His conviction that society is rotten at its base is only the more ardently held, his search for alternative ways of expressing his conviction becomes only the more feverish as a result of suppression. Terror does not alter opinion. On the one hand it reinforces it, on the other it makes the substance of opinion a matter of interest to many who would, otherwise, have had no interest whatever in it. When the United States Customs Department suppressed _Candide_ on the ground that it was an obscene book, they merely stimulated the perverse curiosity of thousands to whom _Candide_ would have remained less than a name. When the British Government prosecuted the Communists for sedition in 1925 the daily reports of the trial, the editorial discussion of its result, made the principles of Communism known to innumerable readers who would never, under other circumstances, have troubled to acquaint themselves with its nature. No state can suppress the human impulse of curiosity, and there is always a special delight, a kind of psychological scarcity-value, in knowledge of the forbidden. No technique of suppression has so far been discovered which does not have the effect of giving wider currency to the thing suppressed than can be attained in any other fashion. But this is only the beginning of the case for freedom of speech. The heresies we may suppress today are the orthodoxies of tomorrow. New truth begins always in a minority of one; it must be someone’s perception before it becomes a general perception. The world gains nothing from a refusal to entertain the possibility that a new idea may be true. Nor can we pick and choose among our suppressions with any prospect of success. It would, indeed, be hardly beyond the mark to affirm that a list of the opinions condemned as wrong or dangerous would be a list of the commonplaces of our time. Most people can see that Nero and Diocletian accomplished nothing by their persecution of Christianity. But every argument against their attitude is an argument also against a similar attitude in other persons. Upon what grounds can we infer prospective gain from persecution of opinion? If the view held is untrue, experience shows that conviction of its untruth is invariably a matter of time; it does not come because authority announces that it is untrue. If the view is true in part only, the separation of truth and falsehood is accomplished most successfully in a free intellectual competition, a process of dissociation by rational criticism, in which those who hold the false opinion are driven to defend their position on rational grounds. If, again, the view held is wholly true, nothing whatever is gained by preventing its expression. Whether it relates to property, or marriage, to religion or the form of the state, by being true it demands a corresponding change in