Science fiction uses generations as guinea pigs in thought experiments: writers will change one important feature of human life, but leave the rest intact, in order to hypothesise how a single, world-rearranging shift might play out. In S M Stirling’s Emberverse series (2004-), a mysterious event alters the laws of physics, neutralising electricity and gunpowder, and the kids who are born after ‘The Change’ – archers, farmers, fighters – are different from the ones who knew the powered world. In Robert Heinlein’s Orphans of the Sky (1963), people living in the closed environment of a multigenerational starship mutiny and kill many of their leaders; years later, their descendants have lost any true knowledge of their situation and believe that their ship is the whole world.

These fictions work because they are controlled experiments. They allow you to shove aside the complexities of life, to isolate one variable, one aspect of human experience. They give you a window into the plasticity of human culture, the impact of big historical events, the exercises of power between young and old, and the way that we make and re-make our worlds through education and tradition.

But in real life, I find generational arguments infuriating. Overly schematised and ridiculously reductive, generation theory is a simplistic way of thinking about the relationship between individuals, society, and history. It encourages us to focus on vague ‘generational personalities’, rather than looking at the confusing diversity of social life. Since I’m a ‘Gen-X’er born in 1977, the conventional wisdom is that I’m supposed to be adaptable, independent, productive, and to have a good work/life balance. Reading these characteristics feels like browsing a horoscope. I see myself in some of these traits, and can even feel a vague thrill of belonging when I read them. But my ‘boomer’ mother is intensely productive; my ‘Greatest Generation’ grandmother still sells old books online at age 90, in what I consider to be the ultimate show of adaptability and independence.

Generational thinking doesn’t frustrate everyone. Indeed, there is a healthy market for pundits who can devise grand theories of generational difference. Neil Howe and William Strauss, authors of Generations: The History of America’s Future, 1584-2069 (1991) and founders of the consulting firm LifeCourse Associates in Virginia, have made a fine living out of generational assessments, but their work reads like a deeply mystical form of historical explanation. (Strauss died in 2007; Howe continues to run the consultancy LifeCourse.) The two have conceived an elaborate and totalising theory of the cycle of generations, which they argue come in four sequential and endlessly repeating archetypes.

In the Strauss-Howe schema, these distinct groups of archetypes follow each other throughout history thus: ‘prophets’ are born near the end of a ‘crisis’; ‘nomads’ are born during an ‘awakening’; ‘heroes’ are born after an ‘awakening’, during an ‘unravelling’; and ‘artists’ are born after an ‘unravelling’, during a ‘crisis’. Strauss and Howe select prominent individuals from each generation, pointing to characteristics that define them as archetypal – heroes are John F Kennedy and Ronald Reagan; artists: Theodore Roosevelt, Woodrow Wilson; prophets: John Winthrop, Abraham Lincoln; nomads: John Adams, Ulysses Grant. Each generation has a common set of personal characteristics and typical life experiences.

plenty of kids at less-privileged schools weren’t intensely worried about grades or planning, like the stereotypical millennial

The archetypal scheme is also a theory of how historical change happens. The LifeCourse idea is that the predominance of each archetype in a given generation triggers the advent of the next (as the consultancy’s website puts it: ‘each youth generation tries to correct or compensate for what it perceives as the excesses of the midlife generation in power’). Besides having a very reductive vision of the universality of human nature, Strauss and Howe are futurists; they predict that a major crisis will occur once every 80 years, restarting the generational cycle. While the pair’s ideas seem far-fetched, they have currency in the marketplace: LifeCourse Associates has consulted for brands such as Nike, Cartoon Network, Viacom and the Ford Motor Company; for universities including Arizona State, Dartmouth, Georgetown and the University of Texas, and for the US Army, too.

The commercial success of this pseudoscientific mumbo-jumbo is irritating, but also troubling. The dominant US thinkers on the generational question tend to flatten social distinctions, relying on cherry-picked examples and reifying a vision of a ‘society’ that’s made up mostly of the white and middle-class. In an article in The Chronicle of Higher Education in 2009 on the pundits and consultants who market information about ‘millennials’ to universities, Eric Hoover described Howe and Strauss’s influential book about that generation, Millennials Rising: The Next Great Generation (2000), as a work ‘based on a hodgepodge of anecdotes, statistics, and pop-culture references’ with the only new empirical evidence being a body of around 600 interviews of high-school seniors, all living in wealthy Fairfax County, Virginia.

Hoover interviewed several people in higher education who voiced their doubts about the utility of Howe and Strauss’s approach. Their replies, informed by their experience teaching college students from across the socioeconomic spectrum, show how useless the schematic understanding of ‘millennials’ looks when you’re working with actual people. Palmer H Muntz, then the director of admissions of Lincoln Christian University in Illinois, noticed that plenty of kids he encountered on visits to less-privileged schools weren’t intensely worried about grades or planning, like the stereotypical millennial. Fred A Bonner II, now at Prairie View A & M University in Texas, pointed out that many of the supposed ‘personality traits’ of coddled and pressured millennials were unrecognisable to his black or Hispanic students, or those who grew up with less money. Siva Vaidhyanathan, a cultural historian and media scholar at the University of Virginia, told Hoover: ‘Generational thinking is just a benign form of bigotry.’

Academics have been chewing over the concept of ‘generations’ for more than a century, and have by and large concluded that generational thinking is bogus. Distinctions between given age groups in a society can be an interesting lens for examination – but only if the person framing the questions is painfully cautious to qualify her terms, set careful parameters, and examine her assumptions.

Writers began creating big theories about generational meaning in the 19th century. By the time the Hungarian-born sociologist Karl Mannheim wrote the formative essay ‘The Problem of Generations’ (1928), he could include 33 references in his bibliography, from European scholars who had been addressing the question since 1862. A pervasive 18th- and 19th-century European intellectual interest in modernisation, progress and change laid the groundwork for assessments of age groups as separate entities whose efforts would bring societies closer, or distance them, from the goals that writers set for their cultures. Then, traumatic and socially significant experiences of revolution and war in the 19th and 20th centuries disposed people to try to understand how such dramatic changes could happen so quickly – and how they might change those who lived through them. Young people began to self-define as fundamentally different from older people, and to take political action based on those generational beliefs.

Mannheim, born in Budapest in 1893, had a life marked by 20th-century political upheaval. He was a student during the First World War, had to leave Hungary for Germany when the Kingdom of Hungary was reinstated in 1920, then had to leave Germany for England when the Nazi regime came to power and he lost his professorship for being Jewish. Despite the huge impact that the historical coincidence of his birth had on his life, Mannheim wrote his 1928 essay in order to temper enthusiasm about the broad generational explanations that were en vogue in the European intellectual community.

It was time, Mannheim wrote, to think more systematically about this attractive way to explain historical change. He wrote that the logical fallacy of the generational approach ‘lay in the attempt to explain the whole dynamic of history from this one factor – an excusable one-sidedness easily explained by the fact that discoverers often tend to be over-enthusiastic about phenomena they are the first to see’.

Mannheim divided the theory of generations, up until his intervention, into two parts. Positivist thinkers – mostly French, and influenced by the philosopher Auguste Comte – had tried to ‘find a general law to express the rhythm of historical development’, in keeping with their project of understanding society empirically in order to rationally direct its course. Looking at the average life course of humans, these thinkers and writers tied the progress – or lack thereof – of human culture directly to this biological limitation, and wondered how things would change if humans lived longer or shorter lives.

Disambiguation between the youth of Fairfax County and young people living in the South Side in Chicago was essential

Romantic theorists of generations – mostly German – went the other way, presenting the character of generations as ‘evidence against the concept of unilinear development in history’, as Mannheim put it in his essay. This school represented generations qualitatively and mystically. They imagined the existence of some kind of force in the ether that bound generations together. Wilhelm Pinder, a German art historian who tried to understand the development of his country’s art generationally, advanced the concept of entelechy – a word coined by Aristotle and developed by the German philosopher Gottfried Leibniz, who wrote in the 17th and early 18th centuries. This word referred to an inner motivation and organisation, what Pinder called ‘an inborn way of experiencing life and the world’, which operated on a metaphysical level and could be shared within a group.

Neither of these models totally satisfied Mannheim, who felt that biological (positivist) or spiritual (romantic) speculations about the nature of ‘secular rhythms’ in history should be advanced with caution. These speculations, he thought, were ‘simply used as a pretext for avoiding research into the nearer and more transparent fabric of social processes and their influence on the phenomenon of generations’. And no set interval of generational spread – 30 years; 15 years – should be accepted as gospel, since intermediate generations always played a part in the development of the generations around them.

Most helpfully for our purposes, Mannheim cautioned the reader to recognise the existence of diverse ‘generation units’. Disambiguation – say, between the present-day youth of Fairfax County and young people living in the Rio Grande Valley in Texas or the South Side in Chicago – was essential. As evidence, he pointed to European peasants living outside of cities in the 18th and 19th centuries, who couldn’t possibly have the same perspective as their urban, educated brethren on the upheavals of revolution. It was tempting, he admitted, to make literary or artistic groups stand in for the rest of their generation, since such self-reflective, highly analytical groups made entelechies really visible. ‘But if we pay exclusive attention to them,’ he warned, ‘we shall not be able really to account for this vector structure of intellectual currents.’

The Canadian-American sociologist Norman Ryder redefined the problem with ‘The Cohort as a Concept in the Study of Social Change’ (1965), which is still widely cited in sociological literature dealing with age, life course and experience. ‘A cohort may be defined as the aggregate of individuals (within some population definition) who experienced the same event within the same time interval,’ Ryder argued. That qualifier – ‘within some population definition’ – was key. Sociologists looking at cohorts could avoid oversimplifying their data by always controlling for other factors relating to social position: geographical location, gender, race, education, occupation.

To assume that a given group of people would be similar because of birthdate, Ryder thought, was to risk committing a fallacy. ‘The burden of proof is on those who insist that the cohort acquires the organised characteristics of some kind of temporal community,’ he wrote. ‘This may be a fruitful hypothesis in the study of small groups of coevals in artistic or political movements but it scarcely applies to more than a small minority of the cohort in a mass society.’

Ryder had harsh words for the theorists he called ‘generationists’. He argued that thinkers about generation on a large scale had made illogical leaps when theorising the relationship between generations and social change. ‘The fact that social change produces intercohort differentiation and thus contributes to inter-generational conflict,’ he argued, ‘cannot justify a theory that social change is produced by that conflict.’ There was no way to prove causality. The end result, he wrote, was that grand generational theories tended toward ‘arithmetical mysticism.’

While sociologists of the past half-century have used Ryder’s cohort concept to see deeper into human experience – structuring their studies using the variable of birthdate along with any number of other defining facts that might shape human lives – some historians have also tried to recover the generational idea by writing about specific cohorts. By mid-century, historians reflecting on their own methodology saw earlier efforts to propose long-term, large-scale generational schemata, such as those of François Mentré, Henri Peyre, and Julián Marías, as hopelessly arbitrary.

The US historian Robert Wohl wrote, in his book Generation of 1914 (1979), about the European intellectuals who self-defined as a group after the Great War. In wrestling with the idea of ‘generation’, Wohl looked at the self-conscious creation of the concept in post-war Europe. Wohl’s key theoretical move was to skirt the question of the existence of a generation, instead making a meta-analysis, looking at the way that cohorts of intellectuals, artists and academics (including Mannheim and the Spanish philosopher José Ortega y Gasset) developed their specific generational consciousness. Wohl studied the formation of the idea, rather than the actuality.

the generation that came of age between 1790 and 1830 was shaped by being the first adults to grow up in the new nation

The people who made up Wohl’s ‘Generation of 1914’ had many similar intellectual obsessions: the casting-off of traditions, an emphasis on action, a prizing of authenticity and avant-garde thought. Yet Wohl took care to point out the differences between units within this ‘generation’, even those separated by only a few years. Slightly older men, who entered the First World War early in the conflict, after establishing nascent careers and while the project of the war was still seen as an honourable one, had a very different experience from those younger soldiers who went straight from school to war. While both groups were later considered part of the ‘Lost Generation’ of British elites, Wohl wrote, the survivors’ social position and attitudes upon their re-entry after the war were quite different.

More recently, some historians have tried to think generationally while rigorously acknowledging the structural limitations of the approach. In her book Inheriting the Revolution: The First Generation of Americans (2000), the US historian Joyce Appleby wrote about the generation that came of age between 1790 and 1830, and was fundamentally shaped by the experience of being the first adults to grow up in the new nation. Religious revival, economic opportunity and democratic politics made their mark on these people, who created their own ideology around what it meant to be a citizen.

The US historian Ira Berlin, in his Generations of Captivity: A History of African-American Slaves (2003), turns the generational lens on a population that has been historically ignored when it comes to discussions of generational ‘character’: enslaved people in the US. Berlin outlines a loose scheme, focusing on the way successive groups of enslaved people reacted to and shaped the conditions of their enslavement. Even within this framework, Berlin identifies differences in cohorts that lived in different geographical areas. His generational distinctions are less about ‘personality’ than they are about shared experience and response. A simple comparison between the stories he tells in this book, and the parallel lives of white Americans who lived during the same time, gives the lie to the utility of the generational concept in identifying universal trends in US history.

As the French historian Pierre Nora wrote in 1996, the careful analyst trying to talk about generations will always struggle: ‘The generational concept would make a wonderfully precise instrument if only its precision didn’t make it impossible to apply to the unclassifiable disorder of reality.’ The problem with transferring historical and sociological ways of thinking about generational change into the public sphere is that ‘unclassifiability’ is both terrifying and boring. Big, sweeping explanations of social change sell. Little, careful studies of same-age cohorts, hemmed in on all sides by rich specificity, do not.

Perhaps the pseudoscientific use of supposed ‘generations’ would irk less if it weren’t so often used to demean the young. Millennials, consultants advise prospective employers, feel entitled to good treatment even in entry-level jobs, because they’ve been overpraised their whole lives. Millennials won’t buckle down and buy cars or houses, economists complain; millennials are lurking in their parents’ basements, The New Yorker cartoon stereotype runs, tweeting and texting and posting selfies and avoiding responsibility.

Actual millennials are fighting back, pointing out that this focus on technology use and supposed personality differences is obscuring the very real (and dire) economic conditions that young people face. ‘Sometimes it’s important to start with numbers,’ Malcolm Harris wrote in the ‘Youth’ edition of The New Inquiry in 2012. ‘When it comes to inter-generational conflict, tied as it is to stories about Oedipus and Hamlet, numbers help ensure we’re speaking of a particular relation rather than a mythic archetype.’ Harris, who will publish a book on the topic this year, pointed out that young people deal with unemployment, overpolicing, lack of economic opportunity, tuition increases, and mountainous student debt.

A popular critique, in the form of the ‘Old-Economy Steve’ meme, shows that Harris is not alone in pointing out the hypocrisy of older public opinion that’s ready to disdain young people facing big social problems. An image of a 1970s-looking teenager (aka old-economy Steve) is overlaid with banner texts such as: ‘Graduates From College. Gets Hired.’; ‘Got My Dream Job. By Responding To A Classified Ad.’; ‘Had A Great Union Job. Unions Are Ruining The Country.’; ‘When I Was In College My Summer Job Paid the Tuition. Tuition Was $400.’ Younger people fume on Tumblr, providing each other with statistics to use in arguments with older people who are convinced they just aren’t ‘trying’ hard enough to get jobs.

Popular millennial backlash against the stereotyping of their generation makes use of the same arguments against generational thinking that sociologists and historians have spent years developing. By drawing attention to the effects of the economic situation on their lives, pointing out that human experience isn’t universal and predictable, and calling upon adults to abandon broad assessments in favour of specific understanding, millennials prove the point: generational thinking is seductive, and for some of us it confirms our preconceived prejudices, but it’s fatally flawed as a mode of understanding the world. Real life is not science fiction.