Free speech is an idea which has at present all the unpopularity of a truism; so that we tend to forget that it was not so very long ago that it had the more practical unpopularity which attaches to a new truth. Ingratitude is surely the chief of the intellectual sins of man. He takes his political benefits for granted, just as he takes the skies and the seasons for granted. He considers the calm o ) f a city street a thing as inevitable as the calm of a forest clearing, whereas it is only kept in peace by a sustained stretch and effort similar to that which keeps up a battle or a fencing match. Just as we forget where we stand in relation to natural phenomena, so we forget it in relation to social phenomena. We forget that the earth is a star, and we forget that free speech is a paradox.
It is not by any means self-evident upon the face of it that an institution like the liberty of speech is right or just. It is not natural or obvious to let a man utter follies and abominations which you believe to be bad for mankind any more than it is natural or obvious to let a man dig up a part of the public road, or infect half a town with typhoid fever. The theory of free speech, that truth is so much larger and stranger and more many-sided than we know of, that it is very much better at all costs to hear every one’s account of it, is a theory which has been justified upon the whole by experiment, but which remains a very daring and even a very surprising theory. It is really one of the great discoveries of the modern time; but, once admitted, it is a principle that does not merely affect politics, but philosophy, ethics, and finally poetry. – from Robert Browning (1903)