ALMOST EVERYBODY WHO CARES ABOUT SCIENCE or ideas knows by now that 2009 is the 150th anniversary of Charles Darwin's On the Origin of Species, as well as the 200th anniversary of its author's birth. Origin of Species is rightly hailed by scientists and non-scientists alike as one of the foundations of modern thought, but it was far from the only important work that came off the presses in 1859. While we might well discount Samuel Smiles's mega-bestseller Self-Help, the eponym of a genre that flourishes like kudzu, the same momentous year brought forth John Stuart Mill's On Liberty, the most passionate treatise on human freedom ever written, and a perennially sacred scripture to the world's civil libertarians.
Like Darwin's great work, On Liberty bases its argument on a single elegant principle, the sort of all-illuminating idea that makes new readers wonder why they never thought of it themselves. In Darwin's case, the key is the evolution of living forms through natural selection. With modifications accumulated over a century and a half of scientific progress, especially in the newer field of genetics, evolutionary theory as Darwin conceived it is now taken for granted by virtually everyone who works in science or accepts its most established findings. Those who still argue against it on religious grounds are far outside the educated mainstream.
Mill's intellectual reputation has followed a somewhat different course. Although he remains a revered figure among feminists and other reformers of many stripes, as well as one of the best known 19th-century philosophers, the argument that propels his most famous work remains as hotly debated today as it was in 1859. Its controversial status owes something to present circumstances--times of economic distress are proverbially unfavorable to individualism and its expression--but also to the uncompromising way Mill (1806-73) framed his position.
"The object of this essay," he wrote near the beginning, "is to assert one very simple principle, as entitled to govern absolutely the dealings of society with the individual in the way of compulsion and control, whether the means used be physical force in the form of legal penalties, or the moral coercion of public opinion. 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. That the only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others."
In his autobiography, Mill correctly predicted that "the Liberty is likely to survive longer than anything else that I have written." Why was this little manifesto neither left behind as a relic in the history of political thought nor embraced as received opinion? The argument, if not the style, seems up to date while still attracting criticism from those on both right and left who want to compel people to take or avoid actions because doing so would be better for them. "The only part of the conduct of anyone, for which he is amenable to society," Mill insists, "is that which concerns others. In the part which merely concerns himself, his independence is, of right, absolute. Over himself, over his own body and mind, the individual is sovereign."
Mill's absolute statement, intended "to govern absolutely," still sounds radical in a way that long-ago political assertions rarely do. Like its author, On Liberty is harder to pin down ideologically than its reputation suggests. Although Mill has often been described as the patron saint of liberalism, his dictum hardly sounds liberal by today's standards. It would rule out requiring people to save for retirement or do a great many other things that modern democratic governments routinely demand of their citizens. On the other hand, few conservatives feel quite comfortable with the notion that sovereign individuals can do whatever they want so long as they cause no harm (a slippery concept) to anyone else. …