C. Freedom of Thought and Discussion (On Liberty, ch. II)
It includes liberty of conscience, liberty of feeling, liberty of opinion and sentiment on scientific, moral, and theological subjects, as well as the liberty to express and publish opinions.
Allowance of these liberties benefits the general good regardless whether opinions are true, false, or partly true and partly false. Since human judgment are fallible, we cannot presume to know with certainty that a particular opinion, no matter how much it conflicts with accepted views, is absolutely false and useless. An opinion, presently not accepted, may turn out later to be true, in which case the common good would have suffered by any suppression of it. Our fallibility is such that we need the freest possible discussion of opposing opinions because our best assurance of the truth of any particular opinion is its shown superiority in tests against all possible opposing opinions. The common good is best served by a climate in which individuals are free to state boldly their opinions rather than suppressing them for fear of public punishment:
“No one can be a great thinker who does not recognize that as a thinker it is his first duty to follow his intellect to whatever conclusions it may lead . . . Truth gains more even by the errors of one who, with due study and preparation, thinks for himself, than b the true opinions of those who only hold them because they do not suffer themselves to think.”
Even if particular opinions are simply false, the common good benefits from their free expression because this forces holders of true opinions to defend and thereby better understand their opinions so they hold them as “living truths” rather than as “dead dogmas.” Generally, the false opinions often contain some portion of truth, in which case their free expression serves the common good as a corrective device leading to the improvement of otherwise acceptable opinions.
