Consider this writing advice from six-time Hugo-Award-winning editor Ben Bova about dialog:
An important rule of thumb when it comes to imparting background information is never to allow the characters to tell each other anything that they already know. It is always tempting to explain things to the reader using this technique, but it is always a mistake.
He gives this example:
“Why John,” he said, “you remember how the expedition team got across Endless Swamp, don’t you?”
“Of course I do,” John replied, chuckling softly. “They glued their snowshoes together to make a raft, and then…”
This is what is commonly called “Maid and Butler” or “As you know, Bob” dialog, although he doesn’t use these terms. He chooses his example well in that it’s just the kind of exchange that an amateur writer would try to get away with. A second’s scrutiny confirms just how awkward it is. The author is using his characters as a mouthpiece for the sake of exposition.
But, respectfully, Bova gets it wrong when he writes, “never allow the characters to tell each other anything that they already know.” Nancy Kress gets closer to the truth when she writes that must be done with a “very light hand” but she also writes, that “there are some times—a very few times” when it is effective. The only exception she allows for is dependent upon the “emotional tone” of the exchange—when characters are angry, patronizing, or self-absorbed.
She provides this example from May Frampton’s “White Wine”:
“You asked me to buy pot roast. Fine; I buy pot roast. Three days later you ask for German vinegar gravy and the pot roast. Fine; I buy all the ingredients for German vinegar gravy. Then you asked if we can have the pot roast and German vinegar gravy on Thursday night. Fine; I leave work early, rush home, and make the roast with German vinegar gravy. And then you’re two hours late and don’t even call! Ethan, what are you trying to do to me?”
But emotional tone isn’t the only factor that can make saying-what’s-already-known effective. Even in situations of heightened emotion, like Tess Barnwell’s tirade above, effectiveness isn’t primarily a of matter anger. Tess is still sufficiently in control of herself to speak deliberately. She tells Ethan what he already knows to justify her anger and explain why she’s been wronged. She feels a need to say all this precisely because he hasn’t been attentive enough to reflect upon the string of unreasonable demands he’s asked of her. He knows all this, but she has to bring it to mind. In short, what’s operating here most fundamentally isn’t emotion, but a rhetorical use of saying-what’s-already-known.
Rhetorical Uses of Saying-What’s-Already-Known
Consider this example:
“You forgot the eggs?” said Amy.
“I left the shopping list you made at home,” said Bob.
“Again?”
“Geez, I’m only human.”
Bob isn’t particularly emotional here, but given that Bob is human, he’s certainly saying-what’s-already-known. He’s using a truism to suggest that the mistake he made isn’t so unusual and that he should be forgiven. It’s a rhetorical move.
Or consider how the writers of the Wheel of Time TV show slipped in this bit of exposition about how the Aes Sedai magic-wielders known are organized:
Liandrin: “Moiraine [a Blue] has flitted back and forth to the Tower for twenty years? Her purpose—the purpose of all Blues—is to gather secrets and discover danger before it strikes at the heart of us, before it strikes at you, Mother. But Trollocs invaded from the west, and Logain’s army swelled from the south, without even a warning from Moiraine. Why? Well, I suggest you ask her, Mother.”
Liandrin’s point is that the Moiraine, and by extension Blue Aes Sedai, have failed in their purpose of gathering and properly disseminating intelligence. All the Aes Sedai around her already know what the duties of Blues are, but it’s important for her argument to bring this fact to bear because she can’t assume that her listeners will follow her train of thought if she doesn’t. Again, it’s rhetorical.
Non-Rhetorical Uses of Saying-What’s-Already-Known
Not every instance of effective saying-what’s-already-known is a rhetorical move. Consider this example inspired by a recent episode of The Expanse:
“Careful, that’s an oscillating phaser. You only get one shot,” said Carl.
“I know,” said Diana.
“Just make it count.”
Here saying-what’s-already-known isn’t particularly rhetorical. Carl isn’t trying to convince anyone of anything. Diana already knows she has to make her one shot count. Carl is just nervous or feels it’s wisest to remind her of what she already knows (Maybe there’s a chance that Diana has confused her weapon with another kind of weapon that is multi-use).
Another important class of effective uses of saying-what’s-already-known is ritual or ceremonial language. Catholics confess their sins to a priest, even if the priest has prior knowledge of such sins, because the sacrament of confession requires that they be said in certain circumstances. Supervisors at holiday parties may give a speech reiterating the accomplishments of their teams. Again, the point isn’t to inform but to make subordinates feel proud of their accomplishments and to convey that leadership values their work. The people of Essos and Westeros weren’t told that Daenerys Targaryen in Game of Thrones was “Mother of Dragons, Breaker of Chains” over and over because they’d somehow forgotten who such a famous woman was but because listing titles is part of the ceremony of introducing royalty.
Conclusion
I hazard that what’s behind Bova’s claim about saying-what’s-already-known, and to a lesser extent Kress’s, is the notion that language is about conveying information—our beliefs, emotions, and the like. If that’s all language is for, there would be no point in saying-what’s-already-known once the speaker believes listeners know what he has to say. But that’s not the case. We use language to convince, to coerce, to promise, to act. There’s a wide expanse of illocutions beyond using our words to teach others.
There are some writers that hawkishly pick out every instance of Maid and Butler dialog and dismiss it as flawed simply because it says-what’s-already-known. Now I admit that most of my examples have not been as heavy-handed as paradigm cases of Maid and Butler dialog. This is because Kress is entirely right when she writes that saying-what’s-already-known requires a light hand, but that subtlety comes from a keen awareness of how we engage in conversation and how we use language. It’s not the kind of knowledge that can be gained by following rules.