Nowadays we condemn all such measures

[235] and disallow the right of the State to interfere with the free expression of opinion.  So deeply is the doctrine of liberty seated in our minds that we find it difficult to make allowances for the coercive practices of our misguided ancestors.  How is this doctrine justified?  It rests on no abstract basis, on no principle independent of society itself, but entirely on considerations of utility.

We saw how Socrates indicated the social value of freedom of discussion.  We saw how Milton observed that such freedom was necessary for the advance of knowledge.  But in the period during which the cause of toleration was fought for and practically won, the argument more generally used was the injustice of punishing a man for opinions which he honestly held and could not help holding, since conviction is not a matter of will; in other words, the argument that error is not a crime and that it is therefore unjust to punish it.  This argument, however, does not prove the case for freedom of discussion.  The advocate of coercion may reply:  We admit that it is unjust to punish a man for private erroneous beliefs; but it is not unjust to forbid the propagation of such beliefs if we are convinced that they are harmful; it is not unjust to punish him, not for holding them, but for publishing them.  The truth

[236] is that, in examining principles, the word just is misleading.  All the virtues are based on experience, physiological or social, and justice is no exception.  Just designates a class of rules or principles of which the social utility has been found by experience to be paramount and which are recognized to be so important as to override all considerations of immediate expediency.  And social utility is the only test.  It is futile, therefore, to say to a Government that it acts unjustly in coercing opinion, unless it is shown that freedom of opinion is a principle of such overmastering social utility as to render other considerations negligible.  Socrates had a true instinct in taking the line that freedom is valuable to society.

The reasoned justification of liberty of thought is due to J. S. Mill, who set it forth in his work On Liberty, published in 1859.  This book treats of liberty in general, and attempts to fix the frontier of the region in which individual freedom should be considered absolute and unassailable.  The second chapter considers liberty of thought and discussion, and if many may think that Mill unduly minimized the functions of society, underrating its claims as against the individual, few will deny the justice of the chief arguments or question the general soundness of his conclusions.

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