Over the past few years of writing and workshopping fiction, I've heard and discussed the word "realism" at some length, and lately I've come to a pretty radical suspicion about it: it does not really exist. That is to say, we talk about realism as though there's an objective rubric against which we can measure a story's relationship to reality, and that that's how we judge whether a story is implausible or outlandish or incredible or otherwise in violation of certain firm parameters of how the universe runs on a narrative level. But this can't quite be the case, because different people have very different plausibility thresholds, which hugely informs the stories they tell and consume. This doesn't have to have anything to do with people's differing ideas about the state of the physical world, I don't think. And it isn't just a question of people having varying levels of willingness to suspend their disbelief, though that's a part of it, or the fact that some people are more bothered than others by the experience of encountering a detail in a story they don't quite buy, though that's a part of it, too. More fundamentally, I think, people have very different conceptions of the essential wackiness of the universe and the lives lived within it, and these conceptions can vary significantly even between people who share the exact same ideas about the nature of physical reality. This is why details that feel perfectly reasonable to one reader can feel mind-bogglingly absurd to another.
This phenomenon is something I've encountered again and again over the years in my own writing. I don't draw much on my autobiography for my fiction, a fact for which the world should be very grateful (Chapter 4: 1995: In Which I Endure the Epic Artistic Ordeal of Trying to Write Little Women: The Musical and Nobody Appreciates My Vision). But, like most writers, I will steal a detail or a situation from my own life if I think it's actually interesting. What I've learned from doing this is that if my life were a book, it would strain the credulity of a lot of readers in spite of its sedate overarching plot (e.g. Chapter 6: 1997: In Which I Try to Pretend Denim Slacks with Elastic Waistbands Are Jeans and Junior High Classmates Remain Unconvinced). Many times the autobiographical details I've used for color in a story — a sudden case of night blindness, the lights in an apartment burning out within a short time frame, a character driven to distraction by a dementia victim's tendency to leave dental floss everywhere — are the details that are scanned as surreal by readers. Yet the episodes in my own life that seem to me to be truly too strange for fiction are truly much stranger than those. I'll never fictionalize the story about how, as a small child, I correctly predicted the due date of the baby my mother would later learn she was carrying, and would then lose (in fiction, such an episode would be mystical and maudlin and annoying). I'll never try to use the fact that my father's favorite tree, an enormous one-hundred-year-old white pine tree, was catastrophically hit by lightning the same year that my father himself was catastrophically hit on the head by a falling branch, leading to the head injury that would lead to his Alzheimer's that would lead to his death (in fiction, this parallel would be too broadly symbolic).
There's nothing more irrelevant to fiction's quality than the question of whether the events it describes actually occurred, of course. But it's interesting to think about how individual's life experiences inform their perceptions of reality, and how these differing perceptions will naturally fuel diverse notions of what "realism" actually is. And this makes perfect sense. After all, our lives shape the characters we're drawn to and the narratives we're interested in — why shouldn't it shape the stories we're willing to believe?