Writing in 1869, John Stuart Mill hadn’t seen just how far Prohibition of alcohol would go in the United States in the 20th century, or how far prohibition of other drugs with recreational potential would go in the 21st century. Even back in the 19th century, people were making the argument that drug use harms other people and so is a legitimate subject for regulation. In On Liberty, Chapter IV, “Of the Limits to the Authority of Society over the Individual” paragraphs 18 and 19, John Stuart Mill is quick to counter the argument by pointing out how this puts no limits on the ability of society to meddle in an individual’s life: 

But, without dwelling upon supposititious cases, there are, in our own day, gross usurpations upon the liberty of private life actually practised, and still greater ones threatened with some expectation of success, and opinions propounded which assert an unlimited right in the public not only to prohibit by law everything which it thinks wrong, but in order to get at what it thinks wrong, to prohibit any number of things which it admits to be innocent.

Under the name of preventing intemperance, the people of one English colony, and of nearly half the United States, have been interdicted by law from making any use whatever of fermented drinks, except for medical purposes: for prohibition of their sale is in fact, as it is intended to be, prohibition of their use. And though the impracticability of executing the law has caused its repeal in several of the States which had adopted it, including the one from which it derives its name, an attempt has notwithstanding been commenced, and is prosecuted with considerable zeal by many of the professed philanthropists, to agitate for a similar law in this country. The association, or “Alliance” as it terms itself, which has been formed for this purpose, has acquired some notoriety through the publicity given to a correspondence between its Secretary and one of the very few English public men who hold that a politician’s opinions ought to be founded on principles. Lord Stanley’s share in this correspondence is calculated to strengthen the hopes already built on him, by those who know how rare such qualities as are manifested in some of his public appearances, unhappily are among those who figure in political life. The organ of the Alliance, who would “deeply deplore the recognition of any principle which could be wrested to justify bigotry and persecution,” undertakes to point out the “broad and impassable barrier” which divides such principles from those of the association. “All matters relating to thought, opinion, conscience, appear to me,” he says, “to be without the sphere of legislation; all pertaining to social act, habit, relation, subject only to a discretionary power vested in the State itself, and not in the individual, to be within it.” No mention is made of a third class, different from either of these, viz. acts and habits which are not social, but individual; although it is to this class, surely, that the act of drinking fermented liquors belongs. Selling fermented liquors, however, is trading, and trading is a social act. But the infringement complained of is not on the liberty of the seller, but on that of the buyer and consumer; since the State might just as well forbid him to drink wine, as purposely make it impossible for him to obtain it. The Secretary, however, says, “I claim, as a citizen, a right to legislate whenever my social rights are invaded by the social act of another.” And now for the definition of these “social rights.” “If anything invades my social rights, certainly the traffic in strong drink does. It destroys my primary right of security, by constantly creating and stimulating social disorder. It invades my right of equality, by deriving a profit from the creation of a misery I am taxed to support. It impedes my right to free moral and intellectual development, by surrounding my path with dangers, and by weakening and demoralizing society, from which I have a right to claim mutual aid and intercourse.” A theory of “social rights,” the like of which probably never before found its way into distinct language: being nothing short of this—that it is the absolute social right of every individual, that every other individual shall act in every respect exactly as he ought; that whosoever fails thereof in the smallest particular, violates my social right, and entitles me to demand from the legislature the removal of the grievance. So monstrous a principle is far more dangerous than any single interference with liberty; there is no violation of liberty which it would not justify; it acknowledges no right to any freedom whatever, except perhaps to that of holding opinions in secret, without ever disclosing them: for, the moment an opinion which I consider noxious passes any one’s lips, it invades all the “social rights” attributed to me by the Alliance. The doctrine ascribes to all mankind a vested interest in each other’s moral, intellectual, and even physical perfection, to be defined by each claimant according to his own standard.

On drug legalization, I am not willing to go as far as John Stuart Mill. In my post Allison Schrager: The Economic Case for the US to Legalize All Drugs, I wrote this:

I agree with Allison that we need to legalize the production and sale of drugs in order to take revenue, and therefore power, away from criminal gangs. But I think it is important that we do whatever we can to drive down the usage of dangerous drugs consistent with taking the drug trade out of the hands of criminals:

• Taxes on dangerous drugs as high as possible without encouraging large-scale smuggling;
• Age limits on drug purchases as strict as consistent with keeping the drug trade out of the hands of illegal gangs;
• Free drug treatment, financed by those taxes;
• Evidence-based public education campaigns against drug use, financed by those taxes;
• Demonization in the media and in polite company of those who (now legally) sell dangerous drugs;
• Mandatory, gruesome warnings like those we have for cigarettes;
• Widespread mandatory drug testing and penalties for use of dangerous drugs—but not for drug possession;
• Strict penalties for driving under the influence of drugs.

Notice that in order to keep the drug trade from going underground, prosecutors must not be allowed to use evidence that an individual purchased or possessed drugs as evidence that he or she used drugs. Evidence of use would have to come from some form of drug testing or from behavior.

(Note: Of course, there needs to be strict rules limiting when testing can legitimately be insisted on, since indiscriminate testing is itself an infringement on liberty.)

How can I justify keeping the use of dangerous drugs illegal? First, by “dangerous drugs” I mean, for example, a drug that has a high probability of causing brain damage if used recreationally in an ongoing way that is easy for someone to fall into. My argument is that, ethically, I am every bit as justified in using time-slices of an individual as the unit for ethical concern as opposed to individuals. If we take that tack, then people’s future selves are like (time-slices of) their children: ethical units that those people now typically have a strong enough altruistic attachment to that we can mostly trust them to try to do the right thing. But just as we are justified in taking children out of the homes of parents who show strong enough evidence of doing something harmful enough to those children that either their competence or the strength of their altruistic link toward those children is in serious doubt, it might under some circumstance be reasonable to take someone’s future self out of that person’s present self’s custody.  

Now, when speaking of taking a person’s future self out of that person’s current self’s custody, it is crucial to distinguish between that person doing something unusual in a way that is consistent between future self and present self and something in which the present self shows a serious lack of “parental” concern for the future self. Here is an example of a test–at least as a thought experiment. Suppose that it were possible to have someone experience the harmful effects of a drug first and then experience the more pleasant, recreational aspects of the drug. Regardless of how you or I view the balance between the positive aspects of the drug and the negative aspects, as long as the individual was willing to experience (in the thought experiment) the harmful effects first and only then experience the more pleasant, recreational aspects, I see no reason or justification for stopping that person.  

Notice that the issue I am raising goes far beyond the question of which drugs to legalize. The principle of deference or non-paternalism to another person’s decisions that has (in my view) such a strong basis at a given point in time becomes weaker when there are harmful effects on an individual in the future, and one recognizes that one is concerned–in what I think is an ethically appropriate way–about that person’s future self in a way that is distinct from caring about the individual seen as a single thing. The idea that time-slices of individuals might be appropriate ethical units means that one cannot necessarily simply accept someone else’s degree of impatience (=the utility discount rate). Given the high costs of any interference with another person–including especially the costs to liberty itself, which is something people care deeply about for themselves–there should be a great deal of deference for another person’s own handling of their own future self. But like the deference we give to parents in the handling of their children, our deference to others in the handling of their own future selves does not deserve the same level of deference as the almost absolute deference we should have to people’s handling of their own current selves, within the private sphere.