Steelman
Masked man fallacy
Also called illicit substitution of identicals, intensional fallacy, hooded man fallacy.
Swapping in another name for the same thing inside “knows”, “believes” or “wants” statements.
What it is
Substituting one name or description for another that refers to the same thing, inside a context about what someone knows, believes, wants or says, where the substitution can change whether the sentence is true.
The pattern
a is b. Person P believes that a is F. Therefore P believes that b is F. (invalid)
An example
“Lois Lane believes Superman can fly. Superman is Clark Kent. So Lois believes Clark Kent can fly.”
Lois doesn’t know Clark is Superman, so she doesn’t believe Clark can fly.
Why it fails
What someone believes depends on how they think of a thing, not just on which thing it is. A person can believe something about a thing under one name and not under another.
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 context is about the thing itself, not anyone’s beliefs: “Superman is in Metropolis; Superman is Clark Kent; so Clark Kent is in Metropolis” is valid.
Try one
A question from the app. The wrong answers are its usual look-alikes.
Group chat. Ben: “Wild news: the anonymous producer DJ Hollow is Kyle from our chem class.” Tara: “No way. Jess has said for years that Kyle has zero musical talent.” Ben: “Ha. Then Jess thinks DJ Hollow has zero talent, and she’s been faking it every time she posts his tracks.”
What’s the flaw?
Jess’s opinion is about Kyle as she knows him; she has no idea he’s DJ Hollow. Swapping one name for the other inside what she thinks gets her views wrong, so there’s no sign she’s faking.
A fair reply
“She didn’t know Kyle was DJ Hollow, so her opinion of Kyle says nothing about what she thinks of Hollow’s tracks.”
Often confused with
- Equivocation
Equivocation uses one word for two things. The masked man fallacy uses two names for one thing.
Where the name comes from
It’s from an ancient Greek puzzle: you know your father but not the masked man, so he isn’t your father, except he is. “Hooded man” is the same puzzle, translated differently. “Illicit substitution of identicals” means swapping in another name for the same thing where that isn’t allowed. “Intensional”, with an s, is philosophers’ word for contexts like “believes”, where how you describe a thing matters.
Attributed to Eubulides of Miletus, a Megarian philosopher of the 4th century BC who is also credited with the paradoxes of the heap and the liar.
Sources
- The Masked Man Fallacy, The Fallacy Files
- Fallacies, Bradley Dowden, Internet Encyclopedia of Philosophy
In the app
Practice spotting it on arguments that sound real.
Steelman has more examples of masked man fallacy, 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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