So far, none of settings, features, or purpose can be used to conclusively identify stories that belong to a single genre, although they are all useful to some extent. Do themes fit in anywhere?
By “theme” I mean an underlying idea or concept that, while not necessarily the immediate focus of a body of work, is still pervasive throughout that work and provides some basis for binding the events and ideas presented into a meaningful whole.
At first glance, themes seem like a handy accordion folder into which we can neatly sort our tales. Hey, they’ll all share the same ideas! Consider the themes of growing up, fitting in, and “finding a place in the world” that are commonly found in the angsty, coming-of-age brat-pack dramas of the 1980s like The Breakfast Club and teen comedies such as Ferris Bueller’s Day Off. Clearly, this theme binds these stories together into a genre. Yes/no?
Um, maybe. But numerous other stories rely on these same themes, which can be found in texts and films as varied as The Last Unicorn, American Beauty, and Let’s Pretend This Never Happened (A Mostly True Memoir) — not exactly peas in a pod. Whether you can justify lumping Pretty in Pink into the same genre as Carrie is going to depend on how loose your notion of genre is. And the broader the notion of genre we adopt, the more likely it is to capture a wide and diverse list of tales that share only a few unimportant similarities.
Essentially, the problem with trying to use themes is that stories across all genres are about people, and characters in stories of all genres do the same kinds of lovely, crazy, and infuriating things that they do in real life. Even when the characters are animals, they are so anthropomorphized that it’s clear the critters are really just stand-ins for humans, a la Wind in the Willows and Animal Farm. ‘Tis a rare tome that does not deal with issues concerning humans and the things they do to themselves, each other, and the world around them.
Themes are really just too general to be of much value for our purposes here. A fantasy novel can paint as bold a picture of class warfare as any history book; a self-help book for the lovelorn can describe the devastating effects of destructive relationships as well as any Bronte sister ever did.
In short, themes may gel the content of a single body of work into a cohesive mass, but they make an awfully runny basis for a genre.