Writer and critic Brad Leithauser, in a beautiful essay in the New Yorker, speaks of looking at stories as "boxes" or as "keyholes." Critics, he suggests, often look at stories as boxes, a kind of puzzle whose "meagre, often hackneyed contents have a way of engineering fresh, refined, resourceful patterns." But if you look at a story as a keyhole, he notes, "you observe some of the characters' movements, you hear a little of their dialogue, but then they step outside your limited purview. They have a reality that outreaches the borders of the page."
For that to happen, though, you need to leave a few unmapped places so the characters can step beyond the boundaries you've sketched, a few strings untied so that the puppets can move freely without your hand. In other words, you need a little ambiguity: a space, however small, for the reader to fit into the piece. A story needs a little room for the reader to interpret, to bring in his or her own perceptions and conceptions.
In almost every workshop, I have a student who sees ambiguity as a very bad thing, an authorial cop-out. This student wants every loose end tied up and every question definitively answered—possibly in a flash-forward epilogue that tells you exactly where everyone ends up and what everything means, summing up the story as neatly as the conclusion of a five-paragraph essay. I think this reaction is often a response not to ambiguity per se, but to ambiguity done badly.
Because all too often, ambiguity in fiction is not the writer's attempt to leave space for the reader—it's the result of the writer's own indecision. Sometimes one of my students will bring a story to workshop that leaves the others scratching their heads. Did the woman and man get back together, or not? Was the cat that showed up at the end the same as the cat at the beginning? "I didn't want to explain too much," the student will often say in the story's defense. "I wanted it to be ambiguous."
When asked, these students generally admit that they don't know, themselves, whether the couple gets back together, or what the deal with the cat is. So they hedge their bets, refusing to give enough evidence one way or another, crossing their fingers that the reader will figure it out and decide for them. Usually, that uncertainty carries over into the story. The reader senses that crucial pieces are missing and ends up confused.
There's a difference between leaving space for the reader to interpret and leaving the reader adrift. To extend Leithauser's phrasing, your story doesn't have to be a hermetically sealed box, but your keyhole should probably be a keyhole, and not a missing side. As the writer, ask yourself: do you know what happens to these characters? Or—be honest—are you hoping the reader will do the work of deciding what happens so you, the writer, don't have to?
I wish I had a litmus test to help diagnose this as you write: are you telling too little, or just enough? But the best test I've found so far is the reader's reaction.
When I talk with people who've read my novel, Everything I Never Told You, some of them ask what the main character was thinking at the moment of her death; others ask what happens to the supporting characters after the final pages. I know what I think happened, so at first I was worried: maybe I'd left out something important. But as we chatted, I realized that these readers weren't confused. On the contrary, they had very firm ideas about what they thought happened. By the end of the book, they felt they knew the characters, and they knew just what they'd think and do. They wanted me to confirm what "really" happened—because they wanted to be right!—but all of them were already positive that they knew.
In fact, some of these readers interpreted particular moments and gestures in ways that surprised me. But I'm okay with this: their interpretations and mine don't have to align. To me, the reader's intense and comfortable certainty—whether you and they see eye-to-eye or not—is a sign that you've left enough space for the reader. The writer's job, after all, is not to dictate meaning, but to give the reader enough pieces to create his or her own satisfying meaning. The story is truly finished—and meaning is made—not when the author adds the last period, but when the reader enters the story and fills that little ambiguous space, completing the circuit, letting the power flow through.