Mill on Freedom of Thought and Expression

Among the many fine accomplishments of the British philosopher John Stuart Mill (1806-1873) was his authorship1 of the classic defense of freedom: On Liberty. In the second chapter of the book, Mill makes a case for allowing others to freely express their views even when those views are almost universally rejected and reviled. Here, in summary, are the four reasons Mill offers:

1. Unpopular opinions may be right

Sometimes the things that we and nearly everyone around us take for granted are flat-out wrong. If this happens to be the case, but we do not permit people to openly state their disagreement and make a case for it, then there is much less of a chance that we ever will realize our errors. “To deny this,” says Mill, “is to assume our own infallibility” (p. 64).

2. Even opinions that are mostly wrong are often partly right

Rarely are our opinions completely right, even when nearly everyone around us agrees with us about them. In Mill’s words, “the general or prevailing opinion on any subject is rarely or never the whole truth” (p.64). Being presented with contrary opinions, even when they are mostly in the wrong, often helps us to notice what isn’t quite right about what we believe, which we can then work on fixing.

3. Even opinions that are completely wrong challenge dogmatism…

Even when our views happen to be completely right, that doesn’t mean that the reasons we have for holding them are good; sometimes, in fact, we are not able to articulate reasons for our views at all. But in such cases our beliefs are not justified. Clashing with contrary views, even completely wrong ones, forces us to search for and articulate good reasons for why we are right and our opponents are wrong. Without this clash, most of us will hold our views “in the manner of a prejudice, with little comprehension or feeling of its rational grounds” (p. 64).

4. … and prevent our beliefs from turning into empty affirmations.

Without any challenge, our opinions—even if they are correct—will become dogmatic, and our affirmation of them will in turn become a “mere formal profession” (p. 64) that we recite with no understanding. But this strips truth of the power to actually benefit the character of those who affirm it. It is only in understanding why particular things are true that we make them our own and feel their full force. Having to argue against contrary views, even when those views are completely wrong, ensures that we assent by reason rather than rote, with all of the benefits that brings.

Questions and complications

1. The reasons above support permitting open argument for deeply unpopular views, but how much do they support allowing the mere assertion of unpopular views without argument? How about trolling? Do Mill’s four reasons apply in such cases, or does one need to look for other reasons?

2. Even Mill doesn’t advocate protecting expression that causes or instigates harm to another person without adequate justification (see pp. 67-68). But there are people who claim to be so sensitive to certain opinions (or even words) that simply hearing them expressed results in deep emotional trauma. Assuming that what such people state is true—and this does seem to be the case in at least some instances—can such cases override Mill’s four reasons?

3. Since Mill’s reasons trade on the idea that it benefits us to hear arguments for views contrary to our own, this suggests that merely allowing free expression is not enough, since opinions can be permitted and yet heard by few. Do Mill’s reasons entail that society is obligated to actively seek out and broadcast arguments for unpopular views, to ensure that they are as widely heard as possible?


1 Possibly together with Harriet Taylor. The evidence, including what Mill himself says about the matter, is equivocal. There is no question that Taylor influenced Mill, but the question of actual co-authorship is not settled.


Mill JS. 1997. On Liberty. Upper-Saddle River, NJ: Prentice Hall. Edited by Curran V. Shields. Original published 1859.