"If all mankind minus one, were of one opinion, and only one person were of the contrary opinion, mankind would be no more justified in silencing that one person, than he, if he had the power, would be justified in silencing mankind." (P 471b)

Mill's argument for the value of free speech:

"But the peculiar evil of silencing the expression of an opinion is, that it is robbing the human race; posterity as well as the existing generation; those who dissent from the opinion, still more than those who hold it. If the opinion is right, they are deprived of the opportunity of exchanging error for truth: If wrong, they lose, what is almost as great a benefit, the clearer perception and livelier impression of truth, produced by its collision with error." (P 471b)

(After this paragraph Pojman leaves out several pages. The following paragraph in Pojman is from the next chapter of Mill's book.)