"On Liberty" is one of the most important books on political thought of the nineteenth century. Fortunately for the 21st century reader it is also one of the most accessible. Mill was a libertarian who chose not to base his defence of liberty on natural rights but on his own revised version of utilitarianism:
"I regard utility as the ultimate appeal on all ethical questions...grounded on the permanent interests of man as a progressive being."
This enables Mill to argue that freedom is needed if man is to be able to explore all the avenues of human development that allow the human race to progress. Total freedom is impossible so what determines the legitimate boundaries of freedom? Mill distinguishes between self-regarding and other-regarding actions. The former should never be interfered with and the latter subject to limitation only if they harm the legitimate rights of others.
For Mill free thought is a self-regarding action which should not be curtailed, and free thought is virtually useless without free speech. He was concerned not only about legal curtailment but also the pressure of social conformity, for he feared a "tyranny of the majority". Mill then proceeds to add a utilitarian argument in favour of free speech: if an opinion is silenced then mankind is necessarily the loser whether the opinion is true or false. He advances a number of arguments to support this, concluding with the claim that a climate of freedom is essential for "great thinkers" and "it is as much, and even more indispensable to enable average human beings to attain the mental stature they are capable of." He has no truck with paternalists seeking to guide people's thoughts in the "right" direction. He was equally hostile to the idea that people had the right not to be offended; hence he opposed the blasphemy law. The single case Mill gives of an acceptable limitation of free speech is the case of corn-dealers and an excited mob. An opinion expressed in a newspaper that corn-dealers are "starvers of the poor" is legitimate, but the same view stated to an angry mob outside the corn-dealer's home may be limited if it "is a positive instigation to a mischievous act."
Mill concedes that actions cannot be as free as speech and seeks to establish the proper limits of freedom of action. Mill proposes that "the sole end for which mankind are warranted...in interfering with the liberty of action of any of their number is self-protection." Because he rejects paternalism he opposes all interference with self-regarding actions. Mill would not have prevented people from taking drugs and he would have led the opposition to seat belt legislation. Mill even rejects state interference with liberty for the sake of crime prevention, e.g. poisons can be used for criminal purposes. Mill was willing to accept a register of their sale but not the banning of them. Mill believes we must not interfere with the "rights"of others but these are narrowly circumscribed and Mill makes it clear that "rights" are not the same as "interests". Hence cut-throat laissez-faire is legitimate. As for moral decency arguments Mill does say that sexual intercourse in public is unacceptable, and though fornication and gambling are acceptable he is in two minds about whether pimps and casino-owners should be allowed to operate. Mill says it is a difficult case that is on the borderline, but adds that in general we must resist attempts to limit behaviour for "moral" reasons because any such action is likely to be the thin end of the wedge.
Though Mill is a very determined anti-paternalist he makes three exceptions: children, primitive societies and the disabled. Children must be guided until they reach maturity and they must be given compulsory education - something not given legislative force until 1871. As for primitive societies we must resist the notion that Mill was a typical Victorian believing in the "white man's burden" or inherent differences between races. He simply observed the reality of the world in the mid-nineteenth century but made it very clear any intervention in backward societies must be temporary with the aim to bring about self-government as soon as possible.
Hence Mill was a much more determined libertarian than most modern writers on the subject. There is just one example where, at first sight, Mill may seem reactionary to modern readers. He wished to restrict the right to have children to those who could prove that they could support them. However, those who today wish others to procreate without restriction do so on the grounds of human rights. Mill based his theories on utilitarianism, and not on rights. There was no welfare state when Mill wrote "On Liberty" and he was concerned with the well-being of children born to people without the means to support them.
In view of the growing restrictions on freedom in Britain this is a book well worth reading again. In particular I like Mill's argument that every restriction on freedom is the thin end of the wedge, providing a justification for further restrictions.