MENTAL MODEL · M0077

The Anna Karenina Principle

TechnicalHigh supportEvolutionary Biology

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Version 1.0.0 · Updated 2026-07-30

CORE DEFINITION

The Anna Karenina principle draws a metaphor from Tolstoy’s opening line: some endeavors need multiple necessary conditions to hold together, while failure can arise from different missing conditions. It is a heuristic for such tasks, not a universal law that success has only one form.

SCAFFOLDING EFFECT

psychology

Reduce cognitive load

Distinguish indispensable conditions from merely helpful factors, check plans for omissions, and compare failure paths. Surface similarities among successes alone do not establish necessity.

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Anchor fast decisions

If success truly requires A, B, and C jointly, the absence of any one defeats that conjunction. Sharing necessary conditions does not make cases alike in other respects, and satisfying all listed necessary conditions may still be insufficient.

MINIMUM ACTION

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Practice this model in one real situation:

For a clearly specified goal, list candidate necessary conditions and explain why success would be impossible without each. Look for counterexamples or alternative routes. Retain justified conditions as checks, mark uncertainty, and evaluate the current plan.

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Source support: Explicit

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en.wikipedia.orghttps://en.wikipedia.org/wiki/Anna_Karenina_principleEN · Explicit
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