On Liberty was enormously popular in the years following its publication. Thomas Hardy recalled later in life that undergraduates in the 1860s knew the book almost by heart. Criticisms of the book in the 19th century came chiefly from thinkers who felt that Mill's concept of liberty left the door open for barbarism, such as James Fitzjames Stephen and Matthew Arnold.
In more recent times, although On Liberty garnered adverse criticism, it has been largely received as an important classic of political thought for its ideas and accessibly lucid style. Denise Evans and Mary L. Onorato summarise the modern reception of On Liberty, stating: "[c]ritics regard his essay On Liberty as a seminal work in the development of British liberalism. Enhanced by his powerful, lucid, and accessible prose style, Mill's writings on government, economics, and logic suggest a model for society that remains compelling and relevant." As one sign of the book's importance, a copy of On Liberty is the symbol of office for the president of the Liberal Democrat Party in England.
Contradiction to utilitarianism
Mill makes it clear throughout On Liberty that he "regard[s] utility as the ultimate appeal on all ethical questions", a standard he inherited from his father, a follower of Jeremy Bentham. Though J.S. Mill claims that all of his principles on liberty appeal to the ultimate authority of utilitarianism, according to Nigel Warburton, much of the essay can seem divorced from his supposed final court of appeals. Mill seems to idealize liberty and rights at the cost of utility. For instance, Mill writes:
|“||If all mankind minus one, were of one opinion, and only one person were of contrary opinion, mankind would be no more justified in silencing that one person, than he, if he had the power, would be justified in silencing mankind.||”|
This claim seems to go against the principle of utilitarianism that it is permissible that one should be harmed so that the majority could benefit. Warburton argues that Mill is likely too optimistic about the outcome of free speech. Warburton claims that there are situations in which it would cause more happiness to suppress truth than to permit it. For example, if a scientist discovered a comet about to kill the planet in a matter of weeks, it may cause more happiness to suppress the truth than to allow society to discover the impending danger. While David Brink concedes that Mill's apparently categorical appeal to rights seems to contradict utilitarianism, he points out that Mill does not believe rights are truly categorical because Mill opposes unrestrained liberty (e.g. offensive public exposure).
Furthermore, David Brink tries to reconcile Mill's system of rights with utilitarianism in three ways:
- Rights are secondary principles to the Greatest Happiness Principle
- Rights are incomparable goods, justifying their categorical enforcement
- Liberty is a good. Thus, those who suppress it are worthy of punishment. Rights deal with the value of punishing/protecting others' interference with liberty, not the actual protection of liberty
Some thinkers have criticised Mill's writing for its apparent narrow or unclear focus in several areas. Mill makes clear that he only considers adults in his writing, failing to account for how irrational members of society, such as children, ought to be treated. Yet Mill's theory relies upon the proper upbringing of children. Plank has asserted that Mill fails to account for physical harm, solely concerning himself with spiritual wellbeing. He also argues that, while much of Mill's theory depends upon a distinction between private and public harm, Mill seems not to have provided a clear focus on or distinction between the private and public realms.
Nigel Warburton states that though Mill encourages religious tolerance, because he does not speak from the perspective of a specific religion, some claim that he does not account for what certain religious beliefs would entail when governing a society. Some religions believe that they have a God given duty to enforce religious norms. For them, it seems impossible for their religious beliefs to be wrong, i.e. the beliefs are infallible. Therefore, according to Warburton, Mill's principle of total freedom of speech may not apply.
Conception of harm
The harm principle is central to the principles in On Liberty. Nigel Warburton says that Mill appears unclear about what constitutes harm. Early in the book, he claims that simply being offensive does not constitute harm. Later, he writes that certain acts which are permissible and harmless in private are worthy of being prohibited in public. This seems to contradict his earlier claim that merely offensive acts do not warrant prohibition because, presumably, the only harm done by a public act which is harmless in private is that it is offensive.
Warburton notes that some people argue that morality is the basis of society, and that society is the basis of individual happiness. Therefore, if morality is undermined, so is individual happiness. Hence, since Mill claims that governments ought to protect the individual's ability to seek happiness, governments ought to intervene in the private realm to enforce moral codes.
Charges of racism and colonialism
Mill is clear that his concern for liberty does not extend to all individuals and all societies. He states that "Despotism is a legitimate mode of government in dealing with barbarians". Contemporary philosophers Domenico Losurdo and David Theo Goldberg have strongly criticised Mill as a racist and an apologist for colonialism.