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Fallacy of Composition

Also Known As: Fallacy of Composition
Informal Fallacy ID: composition

Definition

The fallacy of composition assumes that what is true of the parts must be true of the whole. It erroneously transfers properties from individual components to the aggregate, ignoring emergent properties and interactions. Just because every player on a team is excellent individually does not mean the team will be excellent, because teamwork introduces new dynamics not present at the individual level.

Examples

"Every component in this computer is the fastest available, so this must be the fastest computer ever built." (Ignoring bottlenecks, compatibility, and system architecture.)

A football coach argues: 'Each of our players is individually ranked among the top in the league, so we must be the best team overall.' He ignores how poorly the players work together as a unit.

A music producer insists: 'Every musician on this album is a world-class virtuoso, so this album is guaranteed to be a masterpiece.' He overlooks that clashing styles and poor arrangement can ruin even the most talented lineup.

Formal Logic Pattern
FOL Pattern
The First-Order Logic formula representing this reasoning pattern's logical structure.
FOL (First-Order Logic) uses quantifiers (∀ = for all, ∃ = there exists), connectives (∧ = and, ∨ = or, ⇒ = implies, ¬ = not), and predicates to capture the essential form of a reasoning pattern. For example, the Ad Hominem fallacy: Person(x) ∧ HasFlaw(x) ⇒ Invalid(Claim(x)). These patterns allow automated verification of logical validity.
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Property(part_of(X)) -> Property(X)
Formal Verification:
Formal Verification
Checks whether a reasoning pattern is logically valid or invalid using an automated theorem prover.
Formal verification uses an SMT (Satisfiability Modulo Theories) solver — specifically Z3 — to mathematically check whether an argument's logical structure is valid. Each reasoning pattern is translated into First-Order Logic and tested: Can the premises be true while the conclusion is false? If yes, it's formally invalid. If no, it's formally valid. Many real-world patterns (analogies, heuristics) cannot be fully captured in formal logic — these are marked as not formally decidable, which doesn't mean they're wrong.
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Not formally decidable

Verification Steps
Verification Steps
Binary yes/no questions that an AI must answer to detect a reasoning pattern in a text.
Each of the 452 aspects has verification steps — simple yes/no questions designed to systematically detect whether a pattern appears in a text. For ad hominem: "Does the argument attack a person rather than their claim?" For false dichotomy: "Are only two options presented when more exist?" This ensures consistent, reproducible analysis.
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Binary (yes/no) questions an LLM must answer to identify this aspect:

  1. 1

    Does the argument attribute a property of individual parts to the whole?

    Type: binary
  2. 2

    Is there a valid reason to believe the property scales from parts to the whole?

    Type: binary
  3. 3

    Could the whole have different properties than its individual components?

    Type: binary
Deep Dive
The expandable detail section on each aspect page with examples, psychology, and counter-strategies.
The Deep Dive section provides in-depth information about each aspect: a real-world example showing the pattern in action, an explanation of why it works psychologically, practical advice on how to counter it, alternative names, and links to related aspects.
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Related Aspects

← related to
Mereological Fallacy

The mereological fallacy involves a confusion between the properties of parts and the properties of wholes, but differs from the simpler composition and division fallacies in that it involves a category error about what kind of entity can possess a given property. While composition/division involve incorrect inferences about the same type of property at different levels, the mereological fallacy attributes properties to entities at a level where those properties are conceptually inapplicable — as when neuroscientists say 'the brain decides' or 'the hippocampus remembers,' attributing person-level psychological predicates to sub-personal components.

Hierarchical Context

→ is a Informal Fallacies

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