In Chapter 2, Mill turns to the issue of whether people, either through their government or on their own, should be allowed to coerce or limit anyone else's expression of opinion. Mill emphatically says that such actions are illegitimate. Even if only one person held a particular opinion, mankind would not be justified in silencing him. Silencing these opinions, Mill says, is wrong because it robs "the human race, posterity as well as the existing generation." In particular, it robs those who disagree with these silenced opinions.
Mill then turns to the reasons why humanity is hurt by silencing opinions. His first argument is that the suppressed opinion may be true. He writes that since human beings are not infallible, they have no authority to decide an issue for all people, and to keep others from coming up with their own judgments. Mill asserts that the reason why liberty of opinion is so often in danger is that in practice people tend to be confident in their own rightness, and excluding that, in the infallibility of the world they come in contact with. Mill contends that such confidence is not justified, and that all people are hurt by silencing potentially true ideas.
After presenting his first argument, Mill looks at possible criticisms of his reasoning and responds to them.
First, there is the criticism that even though people may be wrong, they still have a duty to act on their "conscientious conviction." When people are sure that they are right, they would be cowardly not to act on that belief and to allow doctrines to be expressed that they believe will hurt mankind. To this, Mill replies that the only way that a person can be confident that he is right is if there is complete liberty to contradict and disprove his beliefs. Humans have the capacit ...