Internal coherence

Definition

Internal coherence is not realism. A story can be fantastical, absurd, dreamlike and deeply coherent: it just needs to keep the rules it sets. This pact is what lets the reader engage in an invented world — they know what was true in chapter 2 is still true in chapter 22.

What it's for

Internal coherence lets the reader predict (hence anticipate, hence feel) the stakes. Without it, no tension: if magic can do anything, nothing costs anything. It also separates an inhabitable universe from a set: you can imagine living there because its laws are stable. It is the antidote to plot holes and Deus ex machina.

Variants by genre

• Fantasy: magic, economy, geography, cosmology rules.
• SF: established scientific rules (light speed, AI, biology).
• Crime: procedural rules (police, justice, forensics).
• Romance: psychological coherence of characters.
• Historical: period coherence (vocabulary, customs, technology).
• Cozy: social coherence of the village or community.
• YA dystopia: coherence of the political regime.
• Thriller: coherence of timing, distance, means.

Common pitfalls

• Rule introduced late to resolve a scene (disguised deus ex machina).
• Coherence respected 90% of the time, then broken at the climax "because it had to be".
• Coherence sacrificed to push a character forward (contradicted motivation).
• Coherence undocumented → errors between books (saga).
• Confusing coherence with realism: you can be incoherent even in a realistic frame.
• Too many rules: story collapses under its own rigidity.

Examples

• Mistborn (Brandon Sanderson) — model of hard-magic coherence.
• Dune — spice, Bene Gesserit, navigation rules held over 6 books.
• A Song of Ice and Fire — tight political and geographical coherence (until the TV ending).
• The Lord of the Rings — linguistic, cultural, geographical coherence.
• Le Bureau des légendes — espionage procedural coherence.
• The Wire — obsessive institutional coherence.
• Hunger Games — coherence of the Capitol regime.
• Severance (Apple TV) — coherence of a world whose rules unfold.

Writing tips

• Keep a rules log from project start: every rule you set (physics, magic, society) gets a line, a date of first appearance, a source chapter. An untracked rule will be contradicted.
• Run a dedicated "coherence pass" before submission, separate from stylistic polish. Look only for internal contradictions, with the rules log open beside you.
• Check ages, distances, seasons line by line: these are the inconsistencies beta readers spot most often.
• Handle exceptions carefully: every exception to a rule must be flagged in-text, otherwise it reads as a mistake.

Learn more: Coherence across 100,000 words and Complete guide to novel coherence at 100,000 words.

Revision checklist

• Do I have a codex (even informal) of my world's rules?
• Is each rule respected until the climax?
• If I break a rule, is it thematized (the world changes)?
• Do my characters act according to their established psychology?
• Would an expert beta reader of my genre find an inconsistency?