Etymological Fallacy is insisting on a word's original meaning over its current one. It sits in the Cognition dimension (COG) of the Human Behavior Taxonomy™ as element HBT-COG-0279, within the Definition Fallacy family. The core principle: insisting on a word's original meaning over its current one. In incentive terms, it matters because it changes the payoff people perceive before they choose — which means it can be designed for, or exploited.
Scientific Definition
Insisting on a word's original meaning over its current one.
Plain-English Definition
Insisting on a word's original meaning over its current one.
Feynman Explanation
Words move on. Sometimes for better.
Core Principle
Insisting on a word's original meaning over its current one.
Mechanisms
Insisting on a word's original meaning over its current one.
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Inputs (Triggers)
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Outputs (Behaviors)
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Behavioral Signature
Words move on. Sometimes for better.
Examples
- Debating what 'strategy' means in ancient Greek instead of using it to plan.
- Definitional debates that crowd out actual decisions.
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Original analysis from The Incentives Lab — how this element behaves inside real payoff structures.
Why this element matters to incentive design
When this element shows up in a diagnostic, the instinct is to train people out of it. Training rarely moves it. The mechanism underneath it is straightforward: insisting on a word's original meaning over its current one. You can recognize it in the field by its signature: words move on. Sometimes for better. Every element in the Cognition dimension changes the perceived payoff of an action before the action happens, which is exactly where incentive design has leverage.
How it gets exploited
Left undesigned, definitional debates that crowd out actual decisions. It is amplified whenever definitional debates that crowd out actual decisions. Inside organizations that shows up as definitional debates that crowd out actual decisions. The pattern is the same one Goodhart's Law describes: the measurable proxy attracts the effort, and the purpose behind it quietly loses funding.
How the Lab designs around it
The redesign move is to make the desired behavior observable, remove whatever currently pays for its opposite, and attach the reward to the behavior rather than to the noisy outcome downstream of it. Design against it the way you would design against a known failure mode — assume it will appear, and price the exploit before someone finds it.
Famous Experiments
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Design Principles
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Measurement Approaches
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Evidence
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The Perverse Incentive Lens™
How this behavior is exploited — and how to redesign around it.
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Interactive Mini Network
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Knowledge Graph Neighbors
Auto-linked to the rest of the Human Behavior Taxonomy by family, domain, dimension, and shared keywords.
Assuming the conclusion in the premise.
The conclusion is hidden inside the premise.
What's true of the parts is assumed true of the whole.
Because there's no sharp line, no distinction exists.
Quietly redefining a term mid-argument.
What's true of the whole is assumed true of the parts.
Constraining the option set to bias the decision.
Treating two things as comparable when they're not.
Assuming the truth must lie between two extremes.
Deriving 'is' from 'ought.'
Changing success criteria whenever the prior criteria are met.
Deriving 'ought' from 'is.'
Where Etymological Fallacy is cited in the corpus
Essays, field guides, and diagnostics from The Incentives Lab that apply this element.
- EssayGoodhart's Law in the Real World
How measurable proxies capture judgment.
- EssayThe Perverse Incentives Hiding in Your KPIs
Cognitive shortcuts turned into scorecards.
- CourseIncentives 101
The free ten-part primer on reading a payoff structure.
- ReferenceThe incentive glossary
Definitions for every mental model, bias, and fallacy in the corpus.
- ReferenceThe Periodic Table of Human Behavior
The full 1,267-element map this page belongs to.
Questions about Etymological Fallacy
- What is Etymological Fallacy?
- Etymological Fallacy is insisting on a word's original meaning over its current one. It sits in the Cognition dimension (COG) of the Human Behavior Taxonomy™ as element HBT-COG-0279, within the Definition Fallacy family. The core principle: insisting on a word's original meaning over its current one. In incentive terms, it matters because it changes the payoff people perceive before they choose — which means it can be designed for, or exploited.
- What is an example of Etymological Fallacy?
- Definitional debates that crowd out actual decisions. The Incentives Lab catalogs everyday, organizational, and historical instances of this element on its Human Behavior Taxonomy™ page (HBT-COG-0279).
- How is Etymological Fallacy exploited?
- Definitional debates that crowd out actual decisions.
- How do you design around Etymological Fallacy?
- Name the behavior you want in observable terms, remove what currently pays for the opposite, attach the reward to the behavior rather than a lagging proxy, and publish how you will detect gaming.
- Which behavioral dimension does Etymological Fallacy belong to?
- Etymological Fallacy is classified in the Cognition dimension (COG) of the Human Behavior Taxonomy™, family "Definition Fallacy", class "Logical Fallacy". Its permanent identifier is HBT-COG-0279 and its evidence grade is B.