When the US President Richard Nixon announced his ‘war on drugs’ in 1971, there was no need to define the enemy. He meant, as everybody knew, the type of stuff you couldn’t buy in a drugstore. Drugs were trafficked exclusively on ‘the street’, within a subculture that was immediately identifiable (and never going to vote for Nixon anyway). His declaration of war was for the benefit of the majority of voters who saw these drugs, and the people who used them, as a threat to their way of life. If any further clarification was needed, the drugs Nixon had in his sights were the kind that were illegal.

Today, such certainties seem quaint and distant. This May, the UN office on drugs and crime announced that at least 348 ‘legal highs’ are being traded on the global market, a number that dwarfs the total of illegal drugs. This loosely defined cohort of substances is no longer being passed surreptitiously among an underground network of ‘drug users’ but sold to anybody on the internet, at street markets and petrol stations. It is hardly a surprise these days when someone from any stratum of society – police chiefs, corporate executives, royalty – turns out to be a drug user. The war on drugs has conspicuously failed on its own terms: it has not reduced the prevalence of drugs in society, or the harms they cause, or the criminal economy they feed. But it has also, at a deeper level, become incoherent. What is a drug these days?

Consider, for example, the category of stimulants, into which the majority of ‘legal highs’ are bundled. In Nixon’s day there was, on the popular radar at least, only ‘speed’: amphetamine, manufactured by biker gangs for hippies and junkies. This unambiguously criminal trade still thrives, mostly in the more potent form of methamphetamine: the world knows its face from the US TV series Breaking Bad, though it is at least as prevalent these days in Prague, Bangkok or Cape Town. But there are now many stimulants whose provenance is far more ambiguous.

Pharmaceuticals such as modafinil and Adderall have become the stay-awake drugs of choice for students, shiftworkers and the jet-lagged: they can be bought without prescription via the internet, host to a vast and vigorously expanding grey zone between medical and illicit supply. Traditional stimulant plants such as khat or coca leaf remain legal and socially normalised in their places of origin, though they are banned as ‘drugs’ elsewhere. La hoja de coca no es droga! (the coca leaf is not a drug) has become the slogan behind which Andean coca-growers rally, as the UN attempts to eradicate their crops in an effort to block the global supply of cocaine. Meanwhile, caffeine has become the indispensable stimulant of modern life, freely available in concentrated forms such as double espressos and energy shots, and indeed sold legally at 100 per cent purity on the internet, with deadly consequences. ‘Legal’ and ‘illegal’ are no longer adequate terms for making sense of this hyperactive global market.

The unfortunate term ‘legal highs’ reflects this confusion. It has become a cliché to note its imprecision: most of the substances it designates are not strictly legal to sell, while at the same time it never seems to include the obvious candidates – alcohol, caffeine and nicotine. The phrase hasn’t quite outgrown its apologetic inverted commas, yet viable alternatives are thin on the ground: ‘novel psychoactive substance’ (NPS), the clunky circumlocution that is preferred in drug-policy circles, is unlikely to enter common parlance. ‘Legal highs’, for all its inaccuracies, points to a zone beyond the linguistic reach of the war on drugs, that fervid state of mind in which any separation between ‘drugs’ and ‘illegal’ seems like a contradiction in terms. Then again, if that conceptual link breaks down, what does become of the old idea of drugs? When the whiff of criminality finally disperses, what are we left with?

I said ‘old idea’, but the word ‘drug’, at least in the sense that has been familiar throughout our lifetimes, turns out to be a recent coinage, peculiar to the 20th century. The word itself is, of course, centuries old: as a general term for any medication or chemical remedy, it dates back to the 14th century. But its more specific sense – as in ‘drug addict’, ‘drug control’ or ‘drug culture’ – can be dated quite precisely to the years around 1900. And on examination, it proves to be a curious hybrid, bridging two quite separate meanings.

The first is psychoactivity. A ‘drug’ is a substance that acts on the mind, changing the way we think or feel. But this descriptive meaning also carries a strong suggestion of judgment, less easily defined but unmistakably negative. ‘Drug’, in this sense, is a label to be avoided. Thus, according to the industries that produce and promote them, alcohol and tobacco are not drugs; cannabis advocates insist it is not a drug but a herb; and LSD enthusiasts say that it is not a drug but a sacrament. Indigenous users of coca, betel nut or ayahuasca are appalled at the suggestion these substances might be drugs. A cup of tea is psychoactive, but we would only call it a drug if we wished to make a point. An indeterminate white powder bought off the internet, on the other hand, might be legal, but it is undoubtedly still a drug.

Before the 20th century, it would have been difficult to express this idea. Many of today’s ‘drugs’, such as cannabis, cocaine and morphine, were sold in any high-street pharmacy. ‘Heroin’, for instance, emerged in 1898 as Bayer Pharmaceuticals’ new brand of over-the-counter cough medicine. Did the authorities simply turn a blind eye to the dangers that these substances posed? They did not: opium was classified as a poison because of its overdose risk, and cannabis was known to cause mental disturbance in some users. Yet these properties did not confer any exceptional status. And why should they? Even today, there are still plenty of prescription medicines that are toxic, habit-forming or that have deliriant side-effects. What made the drug-drugs special? In the 20th century, they came to be defined by their illegality, but of course they could not have been created by it. Only once certain hostile perceptions about drugs were in place could it make sense to ban them. What caused the perceptions?

We might start with the temperance movement. In the 19th century, alcohol was being recognised as a causal factor in all sorts of social ills, and so temperance campaigns promoted sobriety as the path to personal health, moral virtue and social respectability. Progressive social reformers joined forces with doctors and religious authorities to condemn the habitual intoxication of previous generations. Other intoxicating drugs might not have presented such a widespread problem, but they all got swept up in the same mixture of medical, moral and social opprobrium.

By the late 19th century, consumer groups were campaigning against the heavy doses of opiates and cocaine concealed in patent medicines

Global trade, meanwhile, made imported drugs such as opium and cocaine cheap and abundant; industry refined them into newly potent forms, which an energetic and largely unregulated business sector advertised and distributed to a booming consumer market. At the same time, the hypodermic syringe was transforming medical practice. It allowed doctors – and, increasingly, the general public – to inject large quantities of pure and potentially dangerous opiates such as morphine. This brought a breakthrough in pain relief, but also new risks such as abscesses and blood poisoning and, for some patients, compulsive and self-destructive overuse.

By the late 19th century, consumer groups were campaigning against the heavy doses of opiates and cocaine concealed in patent medicines, and doctors were diagnosing addiction as a medical pathology with serious social consequences. The first uses of ‘drug’ in its modern sense date from this era: in its earliest occurrences, it stood as an abbreviation of phrases such as ‘addictive drug’ or ‘dangerous drug’. Doctors advised governments and the public that injections of powerful narcotics should be confined to professionals. Use without medical supervision was classified as ‘abuse’.

Largely couched in medical terms as it was, the whole notion of ‘drugs’ carried moral and cultural implications from the start. Within the temperance debate, intoxication was an evil in itself and abstinence a corresponding virtue. Also, a good many of the substances that caused concern in the West were associated with immigrant communities: opium in the Chinese districts of San Francisco or London’s docklands, cocaine among the black communities of the southern US. In the racially charged debates of the day, these substances were presented as the ‘degenerate habits’ of ‘inferior races’, a ‘plague’ or ‘contagion’ that might infect the wider population. Such ideas might no longer be explicit, but the drug concept certainly carries a murky sense of the foreign and alien even now. That’s why it rarely applies to the psychoactive substances that we see as part of normal life, whether caffeine in the west, coca in the Andes, or ayahuasca in the Amazon.

During the first years of the 20th century, opium, morphine and cocaine became less socially acceptable, rather as tobacco has in our era. Their use was now viewed through the prism of medical harm, and their users correspondingly started to seem feckless or morally weak. The drugs themselves became, in a sense, ‘legal highs’: not technically prohibited but retreating into the shadows, available only under the counter or from those in the know. And then, once their sale was formally banned in the years around the Great War, ‘drugs’ became a term with legal weight: a specified list of substances that were not merely medically dangerous or culturally foreign, but confined to the criminal classes.

The banning of drugs occasioned strikingly little public debate, certainly compared with the prohibition of alcohol in the US. Then again, the ‘drug problem’ was pretty marginal at that point, and confined to subcultures (ethnic, bohemian, criminal) without a public voice. The only organised resistance to this new language of condemnation came from the pharmaceutical industry, concerned that its legitimate trade was being tarnished by unfortunate associations. What’s now the American Pharmacists Association, pressured by its major corporate sponsors such as Johnson & Johnson, complained about the casual use of terms such as ‘drug evil’, ‘drug fiend’ and ‘drug habit’, and lobbied newspapers to specify the drugs in question as ‘narcotics’ or ‘opiates’.

But ‘drugs’ was too vague and too useful to replace with more precise terms. It conveyed not simply particular chemicals, but a moral position on the use of them by certain people and for certain purposes. This position was eventually enshrined in the legal frameworks that emerged to prohibit them. The 1961 UN Single Convention on Narcotic Drugs, the founding document of the international drug laws, is unique among UN conventions in using the word ‘evil’ to describe the problem it seeks to address.

Legislators celebrated the 1961 Convention as the culmination of a 50-year battle to prohibit drugs, a battle that had begun at the Hague Opium Conference of 1911. Yet with hindsight, 1961 was the moment at which the consensus around the evils of drugs began to fracture. An adventurous postwar generation, the first to be raised as truly global consumers, was awakening to the realisation that alcohol was not the world’s only intoxicant. An international underground was beginning to spread news of hashish-smoking in Morocco and LSD synthesised in Swiss laboratories, as well as Benzedrine pills that propelled truck drivers through the night, and hallucinogenic mushrooms in Mexican mountain villages. For many, the resounding denunciations of drugs as dangerous, foreign and criminal no longer rang quite true. Within a booming youth culture, controlled substances were becoming the talismans of a new morality, an entire view of life that valorised pleasure, experiment and self-discovery.

In a sense, Nixon’s war on drugs was lost before it was even announced. It could have succeeded only by uniting an already polarised society in the belief that drugs were a genuine threat to civilisation, and that there was a genuine possibility of returning to a world without them. These propositions grew ever harder to sell over the intervening decades, as drug use became increasingly normal, while the vast sums of money spent trying to control it not only failed to reduce it, but actually created a global criminal market on a scale that Nixon could never have imagined.

psychiatric diagnoses such as low self-esteem and social anxiety open the door to new ‘feel-good’ drugs designed to enhance confidence and happiness

The problem is not just one of unintended consequences. As the war on drugs has dragged on, the medical, moral and cultural certainties that interlocked so tightly to create the very concept of ‘drugs’ have been drifting out of focus. In medical terms, the category rested on a clear distinction between sanctioned ‘use’ and criminal ‘abuse’. Yet today’s consumers are in practice free to make this distinction themselves. The arrival of online pharmacies means we can all take our chances with the prescription drugs of our choice: generic, pirated, off-label, out of date or semi-legitimately dispensed by doctors and pharmacists on the other side of the world. As a result, the line between pharmaceutical and illicit drugs is blurring. Recent studies in the US have found opiate users moving from prescription drugs such as OxyContin and Vicodin to street heroin and back again, depending on price and availability. As new ‘legal highs’ with opiate-like effects come on-stream, any such line may eventually become impossible to draw.

Within the pharmaceutical industry as a whole, other pressures and trends are conspiring to soften the distinction between recreation and medicine, ‘feeling good’ and ‘feeling better’. Smart drugs and nootropics promise to make us feel ‘better than well’; the broadening of psychiatric diagnoses to encompass conditions such as low self-esteem and social anxiety opens the door to new ‘feel-good’ drugs designed to enhance confidence and happiness. Pop-science catchphrases such as ‘serotonin-booster’ might apply equally to antidepressants or to MDMA. At the cutting edge of brain research, neural network studies are pointing the way towards implants for deep-brain stimulation or brain-embedded fibre-optic cables: a brave new world in which moods and perceptions might be controlled electronically and drugs, good or bad, would be redundant.

At the same time, the cultural landscape in which ‘drugs’ were defined is receding from view. Nixon launched his war on drugs in a country where even cannabis was a profoundly alien substance to almost everybody over the age of 30; today, most Westerners below retirement age recognise drugs, for better or worse, as part of the culture in which they grew up. We have long been comfortable global consumers, seeking out the novel and exotic in everything from food to travel, music to spirituality; our appetite for intoxicants participates in this pursuit of novel sensations, and is explicitly linked to it by corporate advertising that uses the visual lexicon of mind-expanding drugs to sell us everything from energy drinks to smartphones. ‘Drugs’, in its original sense, drew on a reflexive distaste for the culturally alien. This distaste has itself become alien to the inhabitants of the 21st century.

As drugs have swirled into this kaleidoscope of lifestyle and consumer choices, the identity of the ‘drug user’ has slipped out of view. A unitary class of ‘drugs’ depended for its coherence on an identifiable class of users, clearly recognised as deviant. But drug use has long ceased to function as a reliable indicator of class, ethnicity, age, political views or any criminality beyond itself. Plenty of drug users self-identify with confidence these days and, if conspicuous drug ‘scenes’ are easily located, the majority of drug use nevertheless takes place outside them. Buying and selling, the point of greatest visibility and risk for the user, has been rendered virtual: the shady street deals of the past can now be conducted online via PayPal or bitcoin, the incriminating package delivered through the letterbox in an innocuous Jiffy bag.

Though its medical and cultural underpinnings might be shifting, the category of drugs is still firmly defined by the law. At their margins, the drug laws could be starting to reflect the reality of what we might call a post-drug world, but it seems unlikely that they will drive the process. When the drug laws were first passed a century ago, they reflected a cultural shift that had already taken place; we can expect them to be dismantled only after the landscape of a post-drug world is plain for all to see. But even now, it is not hard to discern in outline. Alcohol prohibition, when it eventually collapsed, was superseded by a patchwork of regulatory controls – licensing, insurance, tax – that either existed already or were devised on the basis of pragmatic policy goals.

We can envisage a similar patchwork for a day – however close or distant – when drugs are removed from the ambit of criminal law. In so far as any drug presents medical risks, it requires regulation to minimise them, and a well-established spectrum, from labelling to licensing to prescription, already exists for this purpose. In so far as they constitute a luxury market, we might expect them to be taxed. As with alcohol, in some jurisdictions they might remain illegal by broad popular consent. The prohibition of drugs, including alcohol, was an emergency measure that overrode the logic of pragmatism. The alternative is not another leap in the dark, but a return to the routine regulatory calculus.

But what lies beyond the idea of ‘drugs’ itself? The simple answer is that there is nothing to replace. Behind the term lies a disparate group of chemicals whose varied effects – stimulant, narcotic, psychedelic, euphoriant – offer a more accurate language of description. Value-laden terms, both positive and negative, would doubtless emerge to complement them. A post-drug world would require not a new language but the recovery of an older one. The category of ‘drugs’ was an attempt, characteristic of its historical moment, to separate out good chemicals from bad ones. But as we have known since antiquity, good and evil, virtue and vice are not inherent in a plant or a molecule. Pedanius Dioscorides, the great classical authority on medicine, maintained that no substance is intrinsically good: it all depends on the dose at which it is administered, the use to which it is put, and the intentions behind that use. The Greek term pharmakon could mean both a medicine and a poison: there was no such thing as a harmless remedy, since anything with the power to heal also had the power to harm. All drugs, psychoactive or otherwise, are a technology, a prosthetic that extends our physical and mental reach. Like so many of the other technologies that are transforming our world, their benefits and dangers must ultimately be understood as extensions of ourselves.