Published in 1859, John Stuart Mill's On Liberty presented one of the most eloquent defences of individual freedom in nineteenth-century social and political philosophy and is today perhaps the most widely-read liberal argument in support of the value of liberty. Mill's passionate advocacy of spontaneity, individuality, and diversity, along with his contempt for compulsory uniformity and the despotism of popular opinion, has attracted both admiration and condemnation. While his most vehement contemporary critic, Sir James Fitzjames Stephen, was appalled at the prospect of increasing the liberty of the general population, another of Mill's contemporaries, Thomas Arnold, Jr., warmly praised Mill's commitment to providing guidance to those seeking a life of personal freedom. Appropriately enough, though, Mill would have been pleased by these divergent assessments of his essay, and even more so by the fact that the ideas contained therein continue to spark intense debate across the whole of the political spectrum.

Born in Pentonville, a suburb of London, on May 20, 1806, John Stuart Mill was the eldest son of James Mill (1773-1836). James Mill was a Scottish historian, economist, philosopher and, along with Jeremy Bentham (1748-1832), cofounder of the British utilitarian movement. So great was the elder Mill's fidelity to utilitarianism, it was decided that John would be educated exclusively by his father to ensure his rigorous training in only the most useful of intellectual disciplines. By the age of ten he was reading classical authors in the original Greek and Latin, was proficient in history, algebra and geometry, and soon after began to study logic, politicaleconomy, and law. In 1823 Mill followed in his father's footsteps and secured a position in the examiner's office of the East India Company, where he worked for the next thirty-five years. He was elected to Parliament in 1865 and held the Radical seat for Westminster for the next three years. Mill died in Avignon, France, on May 7, 1873.

It may seem remarkably incongruous that such an influential defence of freedom as On Liberty was written in Victorian Britain, better known for prudishness than for celebration of individualism; however, the common depiction of the Victorian era as simply a period of emotional repression too easily conceals the fact that Mill lived in a time of remarkable changes, including sweeping social reform. Born shortly after the American and French Revolutions, and living during the rapid expansion of liberal democracy, industrialization, nationalism, and colonialism, Mill was truly a child of his age-an ardent advocate of social progress who was also acutely aware that radical change not tempered by justice can threaten the very ideals of collective and individual development. Indeed, Mill's own life embodied the bold, if controversial, events that characterized much of the nineteenth century. In 1823, for instance, Mill was arrested and briefly imprisoned for campaigning in favor of contraception. Several years later Mill suffered a mental "crisis" during which he carried on the routines of his life in a rather mechanical and joyless fashion. Mill recovered from this phase after nearly six months due in large part to his discovery of poetry, an experience which led him to conclude that his father's instruction had been too severe and neglected the importance of cultivating feelings as well as intellect. More significantly, when Mill was twenty-five he met and fell in love with Harriet Taylor (1807-1858), a young married woman and mother of several children. For the next twenty years John and Harriet maintained an intensely passionate-although reputedly platonic-companionship, spending a considerable amount of time traveling together even though Harriet remained married to John Taylor. The relationship was, of course, scandalous to some and it wasn't until 1851, two years after her husband's death, that Harriet and John were married. Yet Harriet exerted a profound influence upon Mill's thinking, in particular helping him to refine his consideration of the practical implications of expanding liberty across a broader range of society. Mill's devotion to Harriet and her egalitarian ideals are made manifest not only in the poignant dedication to her which opens On Liberty, but also in his actions in Parliament, where he vigorously denounced colonialism in Ireland and the West Indies, condemned slavery, proposed wider political rights for the working classes, and advocated universal suffrage.

Mill's desire to have a practical effect on social reform also provided a strong impetus for the writing of On Liberty. It was no accident that Mill was never an academic philosopher content to speculate within the secure confines of the "ivory tower." He was instead a genuine public intellectual, one whose scholarly writings no less than his public actions reflected a deeply personal allegiance to individual freedom and social reform. Nevertheless, Mill's passion was always guided by a, perhaps naïve, faith in rationality and the possibility of directing human progress by means of reasoned debate. Mill's reputation in this regard led the Liberal Prime Minister, William Gladstone, to commemorate him as "the Saint of Rationalism" following his death. In this way, at least, Mill's thought is somewhat dated by his adherence to the Enlightenment faith in the capacity of human knowledge to govern moral and political improvement, a faith severely shaken in the twentieth century by the horrors of genocide and total war. Still, Mill's impressive intellectual powers found a necessary outlet in his prolific and varied writings. Prior to On Liberty, Mill had published A System of Logic (1843) and Principles of Political Economy (1848). Both of these works were extremely well-received, achieving canonical status as textbooks throughout Europe in the nineteenth and early twentieth centuries and earning Mill fame during his lifetime. Two years after the publication of On Liberty, in 1861, Mill published Considerations on Representative Government, which argued for the superiority of representative forms of democratic self-government in maintaining the executive's "complete and ever-operative identity of interest with the governed." There followed, in 1863, Mill's own restatement of utilitarian principles in his Utilitarianism. In 1869, he would publish The Subjection of Women, a sustained critique of the legal, economic, and political disadvantages suffered by women under existing social conditions. Shortly after his death Mill's Autobiography was published, an arrangement carried out by his stepdaughter, Helen Taylor, with whom Mill had developed a loyal personal and working relationship. Mill also wrote a prodigious quantity of essays, reviews, speeches, and journalistic commentaries, all of which have appeared in numerous critical and collected editions.

Although On Liberty was regarded with hostility by many of Mill's contemporaries, it was also widely admired in the years immediately following its publication and helped to consolidate Mill's status as one of the foremost philosophers of his time. Its impact on modern thought has been so immense that generations of liberal thinkers, writers, and artists have come to regard it as nothing less than, in the words of Sir Isaiah Berlin, "the classic statement of the case for individual liberty." Among the many who took inspiration from Mill are notable figures such as the American philosopher and educator John Dewey (1859-1952); the Nobel Prize-winning philosopher Bertrand Russell (1872-1970), who was also Mill's godson; the British novelist and feminist Virginia Woolf (1882-1941); H. L. A. Hart (1907-1992), Professor of Jurisprudence at Oxford; and Julius K. Nyerere (1922-1999), the former President of Tanzania.

In his Autobiography, Mill described On Liberty as "a kind of philosophical text-book of a single truth," namely, that "the only purpose for which power can be rightfully exercised over any member of a civilised community, against his will, is to prevent harm to others. His own good, either physical or moral, is not a sufficient warrant." This "very simple principle," as Mill portrays it in the book itself, is now commonly known as the Harm Principle, and it serves as the basis for his defence of individual freedom. According to Mill, every individual adult should be free from constraint or interference except to the extent that his or her actions might harm others. While society may legitimately restrict the individual in that which "concerns others," each individual should be otherwise free in that which "concerns himself." Isaiah Berlin famously characterized this conception of liberty, whereby freedom consists of doing what one reasonably desires without harming others, as "negative" liberty or freedom from interference. While Mill was concerned about the intrusive powers of government he was also alarmed by the pernicious effects of what Alexis de Tocqueville referred to as "the tyranny of the majority," namely, the despotism that arises when popular public opinion is wielded to silence those holding different ideas. Thus paternalistic intervention is unwarranted, in Mill's estimation, and the individual's liberties of thought and expression, "of tastes and pursuits," and of association are to be free of public control in any civilized society.

Mill's view of liberty has inspired many, yet detractors point to several problematic aspects of his theory. Most obvious is the vagueness of the word "harm" and determining what sorts of things are to be regarded as harmful. Mill was less troubled by such definitional difficulties and suggested that a plain and practical distinction can be made between actions that are physically harmful and opinions that are merely offensive. Unless an opinion is used to incite violence against someone, the views of other people cannot literally cause harm to us no matter how offensive we take those views to be. Rather than resort to censorship, Mill advises, we must learn to practice tolerance. A somewhat more tenacious problem is to be found in Mill's assumption that we can distinguish clearly the self-regarding and other-regarding actions of human beings. Some critics, such as James Fitzjames Stephens, have challenged this assumption by claiming that most if not all of what a person does has the potential to affect and possibly harm other people. If this is so, then the scope for state intervention into the "private" lives of individuals is much broader than Mill was prepared to concede. All the same, Mill was not unaware that it is often complicated to draw a line between what affects only oneself and what might potentially affect others. For this reason he admits that even if an individual's action affects no one else "directly and in the first instance," it may still "affect others through himself."

As a professed utilitarian, it might come as a surprise to learn that Mill's account of liberty also has been criticized for allegedly being inconsistent with the tenets of utilitarianism. The central concern of this doctrine is to achieve the greatest good for the greatest number of individuals, the good being defined as happiness or pleasure. For the utilitarian, the ultimate measure of any action must be its tendency either to maximize happiness or minimize pain. To be consistent, then, critics have charged, Mill must regard liberty as having merely qualified value, conditional upon whether it tends to promote happiness or, conversely, cause pain in the case of any given individual. Liberty cannot be treated as something good in itself for it may be the case that it will produce detrimental consequences for some people. While this criticism may be justly leveled at Benthamite utilitarianism, it disregards a crucial transformation in utilitarianism advanced by Mill. In Mill's opinion, happiness cannot result from seeking pleasure as an end in itself, but must result from the pursuit of other, higher goals. In particular, Mill asserts, the appeal to utility must be "grounded on the permanent interests of man as a progressive being."

It is on this last point especially that Mill's celebrated contribution to moral and political thought must be confirmed. For Mill, the indispensable value of liberty consists of the benefits derived from allowing individuals to make their own choices as to which paths in life to take. In making their own choices in life, individuals are able to develop to the fullest extent possible their human capacities and in doing so achieve personal self-realization. By experimenting in how we live and asking questions about what is best for ourselves, we nurture our mental and moral powers and improve our quality of life. What secures the very possibility that we are able to make ourselves "noble and beautiful objects of contemplation," Mill recognizes, is liberty. Liberty promotes individual and social progress, which leads to fuller, happier lives. While Mill's conception of liberty might take too lightly the sometimes harsh realities of political being, it also expresses a stirring vision of the well-developed life which speaks to some of our deepest human yearnings. For that reason On Liberty exerts a compelling influence upon our time, and will surely remain of enduring value to moral and political thinking.

Patrick Hayden is Lecturer in Political Theory at Victoria University of Wellington. His recent publications include the books John Rawls: Towards a Just World Order and The Philosophy of Human Rights, as well as numerous essays on liberalism, social justice, and political morality.