Steelman
Equivocation
Also called ambiguity fallacy, shifting meaning.
Switching between two meanings of the same word within one argument.
What it is
Using a word or phrase in one sense in one part of an argument and in a different sense in another part, so the argument only appears to hold together.
The pattern
Premise uses term T in sense 1. Another premise (or the conclusion) uses T in sense 2. The conclusion depends on treating the two senses as one.
An example
“Evolution is only a theory, and a theory is just a guess. So evolution is just a guess.”
In science a “theory” is a well-tested explanation of a large body of evidence, like the theory of gravity. In everyday speech it means a hunch. The argument slides from one sense to the other.
Why it fails
Once the two meanings are pulled apart, the premises no longer connect. Each premise may be true in its own sense, but the conclusion needs one sense throughout.
When it’s not a fallacy
Most lists skip this part. Calling a fair point a fallacy is a mistake too.
It can be fair when
- The wordplay is a joke or pun with no argument riding on it.
- The shift in meaning is signaled and the audience isn’t misled.
Try one
A question from the app. The wrong answers are its usual look-alikes.
Skeptic: “I try not to believe anything without evidence, and religious faith asks me to do exactly that.” Believer: “Come on. You sat in that chair without checking the legs. You swallow pills your doctor hands you. You board planes. Faith is how every sensible person gets through the day, which is why it can’t be the enemy of reason.”
What’s the flaw?
The skeptic means faith as believing without evidence. The chair, the doctor and the plane are trust earned by a long track record, which is evidence. The conclusion only works because one word covers both kinds of trust.
A fair reply
“I trust that chair because it’s held me a thousand times. That’s evidence, which is the thing I’m asking for.”
Often confused with
- Amphiboly
Equivocation turns on a word with two meanings. Amphiboly turns on a sentence whose grammar allows two readings.
- Four terms
When the equivocation happens in a syllogism’s middle term, the result is the formal fallacy of four terms.
Where the name comes from
Equivocation comes from Latin words for “equal” and “call”: two meanings called by the same name. To equivocate is to let one word do two jobs in the same argument. “Ambiguity fallacy” names the source, a word with more than one reading, and “shifting meaning” names what happens mid-argument.
Equivocation heads the list of six language-dependent fallacies in Aristotle’s Sophistical Refutations.
Sources
In the app
Practice spotting it on arguments that sound real.
Steelman has more examples of equivocation, how to answer it in a real conversation, and practice rounds that mix it with its look-alikes, so you learn the difference, not just the name. Coming soon to iPhone and Android.
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