Fallacy of Composition
Version 1.0.0 · Updated 2026-07-30
CORE DEFINITION
A concept proposed by Samuelson, referring to the idea that if something is true for a part, it is assumed to be true for the whole simply because it is true for the part. For example, one audience member standing up in a theater can see better, but if everyone stands up, no one can see clearly and everyone is more tired.
SCAFFOLDING EFFECT
Reduce cognitive load
Calibration of macro perspective. It reminds us that when making decisions, we cannot simply superimpose micro-level "correctness." In a company, if every department cuts costs (local optimization), it may lead to the collapse of the entire company (global suboptimality); at the individual level, if everyone saves diligently, it may lead to economic depression (the root of the paradox of thrift).
Anchor fast decisions
Individual rationality may fail when aggregated due to interactions: when everyone performs the same behavior, constraints change (e.g., everyone standing raises the baseline of sight, everyone saving lowers aggregate demand), and the original local benefits are offset or even reversed. The emergent properties of a macro system are not simply the sum of micro properties; ignoring the externality of "others doing the same" leads to the fallacy of composition.
MINIMUM ACTION
In progress 0/1Practice this model in one real situation:
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Source support: Explicit
- en.wikipedia.orghttps://en.wikipedia.org/wiki/Fallacy_of_compositionverified
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