《论自由》The Dread of Skepticism for the Faithless: On Liberty

The claim that an opinion should be protected from public attack is not based solely on its truth, but also on its importance to society. This mode of thinking justifies restraints on discussion based on the usefulness of the opinions and avoids the responsibility of claiming infallibility. However, those who support received opinions often use this justification to their advantage and treat the question of utility as inseparable from the truth. In reality, when the law or public sentiment prohibits the debate of an opinions truth, they are just as intolerant of denying its usefulness. Therefore, there can be no fair discussion of the question of usefulness when arguments vital to it can only be used by one side.