John Stuart Mill was raised as part of an educational experiment to see how much intelligence could be imparted to a child completely shut off from outside influences. As a result of a strict, and lonely,
upbringing, young Mill was reading Greek at three years old and studying the classics, arithmetic and history before seven. He was also inundated with the philosophy of utilitarianism, which he eventually came to view as too objective and cold to be used successfully on human beings. (His odd upbringing probably had something to do with this.) Not suprisingly, by the age of 19, Mill was suffering from massive depression.

Fortunately, he discovered poetry and later largely credited the works of William Wordsworth with having cured him of his illness. After some time in France, where he came in contact with many of the great French minds of the age, Mill began his lifelong investigation into and reformation of the philosophy of utilitarianism—so-called because it promoted an action based on its utility, or usefulness. In fact, the now-familiar phrase, "the greatest good for the greatest number," is part and parcel of utilitarian philosophy.

The basis of utilitarianism is a single, guiding precept: The rightness or wrongness of any action can be judged entirely in terms of its consequences. Motives are, thus, irrelevant—completely the opposite of Kantian theory. Good consequences give pleasure while bad consequences result in pain. (This became known as the "pleasure-pain principle.") According to utilitarianism, the right course of action is the one that promoted the greatest pleasure or minimized the most pain
The result of Mill's work was a utilitarian philosophy much more amenable to the individual and less rigid in its attention to the majority's happiness, and in one of his greatest works, On Liberty (1859), he asserted once and for all the rights of the individual. In addition to his more famous work, Mill is also credited with bringing the rights of women to the forefront in a work entitled The Subjection of Women (1869). In it, Mill argued forcefully for sexual equality, a subject that had been largely ignored since ancient times (except, of course, by women, most especially women philosophers such as Mary Wollstonecraft who wrote vehemently about women's rights in the 18th century).

The Harm Principle

In 1859, John Stewart Mill wrote On Liberty. In it, he laid out the ethical foundation of democratic individualism. At the same time, Mill considered the circumstances under which individual liberty might be justifiably restricted. Under what has come to be known as the harm principle, Mill stated that a person's liberty may justifiably be restricted only in order to prevent harm that the person's actions would cause to others.

Acts of whatever kind, which, without justifiable cause, do harm to others, may be, and in the more important cases absolutely require to be, controlled by the unfavorable sentiments, and, when needful, by the active interference of mankind. The liberty of the individual must be thus far limited; he must not make himself a nuisance to other people.

Following on this principle, the government may limit the freedom of any individual or group if their actions are likely to harm any other part of society. Government prohibitions against murder, theft, rape, and speeding are all examples of this principle. The harm principle is probably the only liberty-limiting principle that is non-controversial and widely accepted.