INKWIRE(7) argument errors INKWIRE(7)
equivocation
Equivocation
One word, two meanings, and the argument switches between them mid-sentence.
NAME
Definition
Equivocation uses a word in one sense in the premise and another sense in the conclusion. The argument looks valid because the same word appears throughout, but the words are different terms wearing the same spelling.
It is not limited to puns. Technical vocabulary is the richest source: "theory", "significant", "model", "law", "natural" and "random" all mean something precise inside a discipline and something much looser outside it.
The fallacy is often unintentional. A writer moves between the everyday and technical senses without noticing, and the conclusion inherits a certainty that only the technical sense could supply.
SIGNALS
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S1
A key term changes meaning across the argument
Substitute a distinct label for each sense — theory-1, theory-2 — and see whether the argument still connects.
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S2
The conclusion uses the strong sense, the premise the weak one
"It is only a theory" slides from the everyday sense (a guess) to the technical sense (a well-tested framework) and then back, taking the prestige with it.
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S3
The middle term is not identical in both premises
In categorical form, a syllogism with four terms instead of three is invalid. Equivocation is how the fourth term hides.
Three checks, in order
- Define every load-bearing word twice: once as used in the premise, once as used in the conclusion.
- Ask whether substituting a synonym for one of the senses preserves the argument. If it collapses, the term was doing two jobs.
- Ask which sense the conclusion needs, then check that the premise supplies that sense.
Where the link breaks
| Term | Sense inside the field |
|---|---|
| Theory | A tested explanatory framework |
| Significant | Unlikely under a stated null model |
| Random | Described by a probability distribution |
| Law | A regularity that holds so far |
EXAMPLES
Evolution is only a theory, and a theory is just an educated guess, so it should not be taught as fact.
Why it fails
In everyday speech "theory" means a hunch. In science it means an explanatory framework that has survived repeated testing and coordinates a large body of evidence. The argument uses the scientific word to name the thing and the everyday sense to grade it.
Kindred entries
- [F] begging-question The conclusion is loaded into the premise, so the argument travels in a circle.
- [F] false-dilemma Two options are presented as the only ones, so rejecting one awards the other.
- index — /t/fallacy/
[+] Notes and objections 3
- Is every ambiguous word a fallacy?
- No. Ambiguity is a property of language, not an error of reasoning. It becomes a fallacy when the argument's validity depends on the shift being unnoticed.
- How is this different from a metaphor?
- A metaphor announces the transfer of sense. Equivocation conceals it, and then draws a conclusion as though no transfer had occurred.
- What is the fastest repair in a live argument?
- Ask the speaker to define the contested word in one sentence. If they cannot, the argument was resting on the ambiguity; if they can, you now have something checkable.
Scope — Reference material for reading arguments, not professional advice.