A gun hung on the wall in Act I must fire by Act III — and nothing may fire that was never hung. Chekhov’s law of narrative economy, made checkable beside Propp: a story is a time-ordered list of events; some PLANT an element, some FIRE it. It is economical iff plants and firings form a time-respecting bijection — every plant fires, nothing fires unplanted, and a plant precedes its firing. The blue team builds the law; the red team smuggles a dangling gun past it.
source Anton Chekhov, from his letters, c.1889 — the pistol formulation appears in his correspondence (e.g. to A. S. Lazarev-Gruzinsky, 1 Nov 1889); the phrasing “remove everything that has no relevance to the story” is reported by S. Shchukin’s memoir. Narrative economy. Room: THE NOVEL. Rendered as structure, not invented.
Late 1880s, Russia: Chekhov, a working doctor writing tales and one-act plays, keeps telling younger writers the same thing — a story is not a room you may furnish freely. Everything shown makes a promise to the reader; an unkept promise is a wasted element.
The 1889 letter puts it as a loaded rifle on the stage that must go off; the popular paraphrase is the pistol on the wall in the first act that must be fired in a later one — otherwise it should not hang there at all. The wider maxim, reported by Shchukin: “remove everything that has no relevance to the story.” Economy, not decoration.
Strip the drama away and the law is two clauses over a list of events:
(1) Every plant fires. An element shown must be paid off — no dangling gun.
(2) Nothing fires unplanted. A payoff must have been set up — no deus ex machina.
Together they say: the map plant → fire is a bijection — onto (rule 1) and one-to-one from real setups (rule 2). The centre engine is exactly that matching.
The bijection is not enough: it must respect time. A gun cannot fire in Act I and be hung in Act II. So the matching adds one order constraint: for every element, its plant index < its fire index.
The checker walks the story once, left to right, holding open plants; a fire matches only a plant already seen. A fire with no open plant is a fault at that instant — the time law and the bijection are enforced in the same pass.
On load the blue team re-runs the law on four known stories: a matched story is accepted, a dangling-gun story is rejected, a deus-ex-machina story is rejected, a fire-before-plant story is rejected. If red drops rule (1) at window 6, this badge is where it turns red.
A story is events in time order. Append a plant or a fire of any element; order is exactly the order you add them. Presets load the four canonical shapes.
One pass. Each plant is held open; each fire must close an open plant of the same element. A fire with none open is a fault the instant it fires; any plant still open at the end is a dangling gun.
| t | event | element | ok? |
|---|
The matching (plant → fire):
LINEAGE. Chekhov’s economy → Propp’s functions (the plant/fire pairing is a promise-and-payoff, as villainy→liquidation is a Propp pair) → the screenwriter’s setup / payoff. A matched story above is the shape all three certify: nothing shown is wasted, nothing paid off was unearned.
So the engine is exact on Chekhov’s contract and silent on the herring’s. Read its verdict inside that contract, not outside it.
“Realism means include everything — life is full of irrelevant detail.” Cut. Chekhov’s realism is ruthless economy: the detail that goes nowhere is removed, not kept for texture. The wall must earn its gun.
“A twist is best when nothing set it up.” Cut. That is deus ex machina — rule (2) forbids it. A payoff with no plant is a cheat, not a surprise.
“The gun is just a metaphor; it proves nothing.” Cut. It reduces to a time-respecting bijection on events — and the panel runs it live.
The red move: drop rule (1). Allow dangling guns — stop requiring that every plant fire. Now a story that hangs a gun and never fires it passes as “economical.” Chekhov forbids exactly that wasted element, so the witness (9), which demands the dangling story be rejected, turns red.
With rule (1) dropped, “economical?” degenerates into “did every firing have a setup?” — the unfired gun on the wall stops counting as waste. The attack is real, and the witness catches it.