And since there are few mental attributes more rare than that judicial faculty which can sit in intelligent judgment between two sides of a question, of which only one is represented by an advocate before it, truth has no chance but in proportion as every side of it, every opinion which embodies any fraction of the truth, not only finds advocates, but is so advocated as to be listened to.

We have now recognised the necessity to the mental well-being of mankind (on which all their other well-being depends) of freedom of opinion, and freedom of the expression of opinion, on four distinct grounds; which we will now briefly recapitulate.

First, if any opinion is compelled to silence, that opinion may, for aught we can certainly know, be true. To deny this is to assume our own infallibility.