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. ...