J. S. Mill agreed with Bentham on the basic principle of utility, namely that “Actions are right in proportion as they tend to promote happiness, wrong as they tend to promote the reverse of happiness. By happiness is intended pleasure and the absence of pain; by unhappiness, pain, and the privation of pleasure.” But Mill made a distinction that Bentham did not: Mill distinguished between the “quality” of pleasures, not just the “quantity” as Bentham had done in his hedonic calculus.

Mill wrote Utilitarianism in response to criticisms abut Jeremy Bentham's hedonistic version of utilitarianism, which failed to differentiate between the kinds and quality of different pleasures and — because of its talk of pleasures — had received the name of a “pig philosophy.”

Mill responded by describing a different theory of happiness. Human beings have faculties more elevated than the animal appetites. You cannot measure pleasures on quantity alone, but must include quality.

Of two pleasures, if there be one to which all or almost all who have experience of both give a decided preference, … that is the more desirable pleasure…. Now, it is an unquestionable fact that those who are equally acquainted with, and equally capable of appreciating and enjoying, both, do give a most marked preference to the manner of existence which employs their higher faculties. Few human beings would consent to be changed into any of the lower animals, for a promise of the fullest allowance of a beast's pleasures; no intelligent being would consent to be a fool, no instructed person would be an ignoramus, no person of feeling and conscience would be selfish and base, even though they should be persuaded that the fool, the dunce, or the rascal is better satisfied with his lot than they are with theirs.”

Since Mill has come down on the side of Socrates instead of the fool, he has separated mental pleasures, which he called “higher” pleasures, from physical pleasures, which he implies are “lower” pleasures.

Mill's On Liberty

Mill worked with his wife Harriet Taylor on On Liberty (1859). Mill wrote, “The object of this Essay is to assert one very simple principle. … That principle is, that the sole end for which mankind are warranted, individually or collectively, in interfering with the liberty of action of any of their number, is self-protection.” In short, individuals have the freedom to express what they want in speech or writing, to adopt their own tastes and pursuits, and to shape the lifestyle they desire, as long as they do not harm others.

Mill's discussion of freedom first takes up the issue of the right to free expression and discussion of ideas. He maintains that society is harmed by the suppression of free speech regardless of whether the ideas in question are true or false. For one, even unpopular ideas that are censored might in fact be true.

Finally, dissenters from any viewpoint will bring forth fresh challenges to ideas and force people to re-examine grounds for their convictions. Without this exercise, our “true opinion will become a dead dogma, not a living truth.”

Free speech that caused immediate harm could be restricted. You cannot shout “fire” in a crowded theater. Mill's defense of personal liberty is rooted in utility, being based on what will promote the social good and prevent harm. His example is:

An opinion that corn-dealers are starvers of poor ought to be accommodated when simply circulated through the press, but may justly incur punishment when delivered orally to an excited mob assembled before the house of a corn-dealer.

Mill is pointing out that when it comes to free speech, context matters. This principle is similar to the “clear and present danger” criterion that the U.S. Supreme Court uses to determine when free speech may be limited.

The Public and Private Spheres

The example of the corn-dealers and shouting fire in the crowded theater show that Mill recognized a difference between public and private behavior. What you do in the “public sphere” is subject to censure. What you do in private is your own business. About this private sphere Mill writes:

There is a sphere of action in which society, as distinguished from the individual, has, if any, only an indirect interest; comprehending all that portion of a person's life and conduct which affects only himself, or, if it also affects others, only with their free, voluntary, and undeceived consent and participation. … This, then, is the appropriate region of human liberty. It comprises, first, the inward domain of consciousness; demanding liberty of conscience, in the most comprehensive sense; liberty of thought and feeling; absolute freedom of opinion and sentiment on all subjects, practical or speculative, scientific, moral, or theological. The liberty of expressing and publishing opinions may seem to fall under a different principle, since it belongs to that part of the conduct of an individual which concerns other people; but, being almost of as much importance as the liberty of thought itself, and resting in great part on the same reasons, is practically inseparable from it.

Added to this freedom of expression is “the liberty of tastes and pursuits; of framing the plan of our life to suit our own character; of doing as we like.” In addition, “There is the liberty for individuals to unite, for any purpose not involving harm to others.” In sum, “No society in which these liberties are not, on the whole, respected, is free, whatever may be the form of government; and none if completely free in which they do not exist absolute and unqualified.” A century and a half after Mill wrote, his thoughts still hold true: namely that censorship, intolerance, and imposed conformity are some of the greatest dangers that a society can face.