Hugh McLachlan: Mill makes us mull more on mephedrone

He was deeply concerned about "the potential criminalisation of increasing numbers of young people". This raises the general question of what the role of the criminal law should be. What is the justification for prohibiting particular actions and for punishing those who commit them?

The proposed "harm principle" of John Stuart Mill, given in his stimulating essay On Liberty, is a useful starting point for considering this matter systematically. According to him: "…. 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."

He further specifies that: "His own good, either physical or moral, is not a sufficient warrant. He cannot rightfully be compelled to do or forbear because it will be better for him to do so, because it will make him happier, because, in the opinion of others, to do so would be wise, or even right."

We may remonstrate with people, according to Mill, and try to persuade them of the error of their ways. However, as long as they are rational adults who are acting voluntarily, we should allow them to make their own mistakes.

Mill draws a distinction between those actions which concern other people and those which concern only the actor himself. With regard to the latter, according to Mill, the individual is not answerable to society and should be sovereign. However, this sort of distinction is controversial. Some people argue that it is not a meaningful one and that all of our actions can potentially affect other people one way or another. Hence, some people feel that it is justifiable to criminalise the taking of drugs even although drug-taking might appear to be an individualistic action.

In response, it should be said that harm is a necessary but not a sufficient condition for restricting the liberty of the individual, according to any reasonable interpretation of Mill's principle. Adult, rational human beings should be allowed to do what they choose to do if, but not only if, their actions do not harm other people. Even if their actions indirectly harm other people, their actions should still often be permitted.

What counts as "harm"? What does it mean to say that an action "concerns" other people? These are awkward questions for a supporter of Mill's position.

The distinction Mill wants to make is not merely between those actions which affect other people and those actions which affect only the actor himself. He wants to distinguish between actions which breach the rights of other people and actions which do not breach their rights, whether or not they affect the other people adversely.

He writes: "With regard to the merely contingent or... constructive injury which a person causes to society, by conduct which neither violates any specific duty to the public... or to any individual except himself, the inconvenience is one society can afford to bear for the sake of the greater good of human freedom."

This distinction, although difficult to make in practice, is of crucial importance. For instance, it could be the case that those who vote for candidates of one or other of the major political parties harm the rest of us if the government they help to elect makes a bigger hash of things than an alternative government would have made. However, it does not follow that such voting behaviour should be a crime. Our rights are not violated by such an action even if our interests are damaged.

In an obvious sense, it concerns others if you live to a great age and enjoy for a long time a state pension and publicly funded healthcare. It concerns others if you do things that lead to using the resources of the NHS or any other public funds. It concerns others, harms them one might say, if people climb mountains or jog and get injured or take drugs and become ill and need expensive hospital treatment. However, it does not follow that taking drugs, climbing mountains or jogging should, on that account, be criminal offences.

From what he says about alcohol, we can apply Mill's view to the taking of drugs. He thinks that if people neglect their duties because they are drunk, they should be punished for neglecting their duties but not for the drunkenness as such, which is their own business. Similarly, it might be suggested that people should not be punished for or prohibited from taking drugs although they could be rightly punished for any harmful actions to others which are a consequence of their drug-taking.

We might, as the saying goes, be tough on the crimes, but the causes of the crimes are not always our business to regulate or punish.

There is a strong case for saying that things should always be legally available for sale to the public under, but only under, certain conditions. It is debatable whether or not these conditions could prevail in the case of some particular drugs. Whether the possession and consumption of drugs should be criminal offences is another matter. For instance, to say that it should be a crime to sell cigarettes to a minor is not to say that it should be a crime for a minor to smoke or be in possession of a cigarette.

Actions should be legally permitted unless there is a justification for prohibiting them and for punishing those who perform the actions. Prohibition and punishment often is justifiable. However, the point is that it requires to be justified or it stands condemned. The onus is always on the banners to justify the bans. When is prohibition and punishment justifiable? If we reject Mill's harm principle, we have the problem of suggesting what to put in its place.

Mill raises a very challenging issue. To punish people for taking drugs because drugs are harmful to the drug-takers is perverse. To punish people for taking drugs in order to deter other people from taking drugs is unfair and unjust. The only acceptable justification for punishment is that the people who are punished deserve the punishment. It is not easy to see how we can justify punishing people who have not harmed others in such a way that their rights are infringed. Why else would they deserve punishment? Why else would we be justified in meting it out?

Hugh V McLachlan is professor of applied philosophy at the School of Law and Social Sciences at Glasgow Caledonian University.