Extrapolation Engine

Extrapolation Engine — And Then What?

The difference between a world that feels invented and one that feels discovered is extrapolation depth. Most worldbuilders define a rule and explore one consequence. Great worldbuilders trace that rule through four or five layers of implication until the consequences are surprising but inevitable.

This skill provides the methodology for systematic extrapolation — the "And Then What?" drill.

The Core Method

Step 1: State the Point of Difference

One clear statement of what's different in this world:

"Faster-than-light travel exists, but communication cannot exceed light speed."

Step 2: First-Order Consequences (Obvious)

What directly follows from the rule? These are the consequences anyone would think of:

• Ships arrive before their own messages
• No real-time coordination across distances
• Military commanders have total autonomy in the field
• News is always old

Step 3: Second-Order Consequences (Interesting)

What follows from the first-order consequences? This is where most worldbuilders stop, but the good stuff is just starting:

• From "commanders have autonomy": Military culture values independent judgment over obedience → officer training emphasizes decision-making, not discipline → the military becomes a source of political leaders who think independently → civilian governance fears military ambition
• From "news is always old": Markets can't respond to distant events in real time → local economies must be self-sufficient enough to survive shocks → economic autarky is rational → trade is high-value goods only (worth the risk of delayed information)

Step 4: Third-Order Consequences (Surprising)

What follows from the second-order consequences? These are the insights that make a reader think "I never would have thought of that, but it's obviously true":

• From "military produces independent political leaders": The most dangerous person in the empire is a successful admiral returning from a distant campaign → the empire develops rituals for reintegrating returning commanders → these rituals are actually surveillance and disarmament protocols disguised as honors → the parade route is designed to separate the commander from their loyal troops
• From "trade is high-value only": Cultures diverge faster because low-value cultural exchange (books, music, fashion) doesn't cross the gap → after a century, a colony feels like a foreign country → after a millennium, it IS a foreign country → "the empire" is a polite fiction maintained by trade agreements, not actual political unity

Step 5: Fourth-Order and Beyond

Keep going until the consequences start contradicting each other or becoming absurd. The contradictions are often the most interesting — they reveal tensions in the world that can drive plot.

The Domain Cascade

For any axiom, trace consequences across these domains:

AXIOM: [state the rule]
    │
    ├── SOCIAL: How does this change daily life?
    │   └── And then what? → [2nd order]
    │       └── And then what? → [3rd order]
    │
    ├── ECONOMIC: How does this change trade, work, wealth?
    │   └── And then what? → ...
    │
    ├── POLITICAL: How does this change governance and power?
    │   └── And then what? → ...
    │
    ├── MILITARY: How does this change war and defense?
    │   └── And then what? → ...
    │
    ├── CULTURAL: How does this change art, values, identity?
    │   └── And then what? → ...
    │
    ├── RELIGIOUS: How does this change belief and cosmology?
    │   └── And then what? → ...
    │
    ├── ECOLOGICAL: How does this change the natural world?
    │   └── And then what? → ...
    │
    └── TECHNOLOGICAL: How does this change what's possible to build?
        └── And then what? → ...

You don't need to go deep in every domain for every axiom. But scanning all eight domains ensures you don't miss a cascade that would make the world richer.

Interaction Effects

The most powerful extrapolations come from two axioms interacting:

Axiom A: "The fantasy system costs memory." Axiom B: "Communication is slower than travel."

Interaction: Powerful magic users have fragmented memories AND can't check their records because news travels slowly. They're powerful but unreliable narrators of their own history. Institutional knowledge must be maintained by non-users — creating a class of "rememberers" who serve magic users. The rememberers become politically powerful because they control what the users think they know.

When you have 3+ axioms, the interaction space becomes rich enough that the world starts generating its own stories. You stop inventing and start discovering.

The Sufficiency Test

An axiom has been sufficiently extrapolated when:

1. It affects at least 4 domains from the cascade above
2. It creates at least one contradiction that generates narrative tension
3. It produces at least one surprise — a consequence you didn't expect when you started
4. A reader could not remove it without the world collapsing (it's load-bearing, not decorative)

If an axiom fails the sufficiency test, either extrapolate deeper or reconsider whether it's truly an axiom. Axioms that don't propagate are decoration.

Common Mistakes

1. Stopping at first-order. "Magic exists, so there are wizards." That's first-order. What do the wizards do to the economy? To politics? To the concept of privacy? Go deeper.
2. Selective consequences. "FTL exists for travel but society is otherwise unchanged." FTL would transform everything — trade, war, colonization, governance, cultural exchange, privacy, espionage. You can't change one thing and leave everything else static.
3. Consequence-proof institutions. "The king rules despite everyone having telekinesis." Why hasn't someone just picked him up and thrown him? If the institution survives, there must be a structural reason — and that reason is more interesting than the institution.
4. Infinite extrapolation. At some point, consequences become too speculative to be useful. Four orders of extrapolation is usually sufficient. Beyond that, you're writing fan fiction about your own world.