#237: Masked-Man Fallacy, Ambiguity & False Inference

3 Ideas in 2 Minutes on Logical Errors

I. Masked-Man Fallacy

It took me a while to wrap my head around the Masked-Man Fallacy, so bear with me here. Consider the following paradox:

[S]uppose that you see a man but don’t recognize him as your father because he’s wearing a mask — perhaps it’s Hallowe’en. So, you don’t know who the masked man is, but you do know who your father is, yet your father and the masked man are one and the same. Therefore, you both know and don’t know who your father is, which is paradoxical. The solution to the paradox is to realize that the argument just given is fallacious.

—Fallacy Files, The Masked Man Fallacy

Put differently, the Masked-Man Fallacy happens when someone treats a person under one description (your father) as if they must be identical to that same person under another description (the man with the mask). Even though the two descriptions convey different information.

Why is that so? Because knowledge and beliefs are also about appearances and descriptions, not just facts. Ignoring this leads people to draw false conclusions about identity, even though there is no real contradiction.

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II. Ambiguity

Ambiguity as a logical fallacy happens when someone uses a word or phrase with more than one meaning and quietly switches between those meanings to mislead. The argument sounds reasonable at first, but it works only because the audience understands the term one way while the speaker later relies on another. This is especially common in advertising, where vague language makes claims seem stronger than they really are.

Take any product that features the phrase “recommended by doctors”. Most people hear this as “widely endorsed by the medical profession after careful testing.” In reality, it might just mean that two doctors in Canberra were sent free samples, didn’t hate it (and the paycheck), and gave a thumbs-up on WhatsApp. Suddenly, the word “recommended” does a lot of heavy lifting. And the claim shrinks. A lot.

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III. False Inference

In his dying moments, Elliott Marsdon (Alan Rickman) is in disbelief. He only forced Matthew Quigley (Tom Selleck) to a duel because he thought the sharpshooter wasn’t good with revolvers. Quigley, though, is not only a quick drawer but also a stickler for logic and the finer details of linguistics. Hence, his iconic line from the Western Quigley Down Under (1990):

I said, I never had much use for one. Never said I didn’t know how to use it.

Marsdon conflated preference with competence. Quigley’s favouring of his Sharps rifle didn’t mean he wasn’t as fast and accurate with a revolver. Elliott’s arrogance made him commit a False Inference.

The logical error happens when someone reaches a conclusion that doesn’t logically follow from the available information. Because we rely on assumptions or incomplete evidence, we fill in gaps without realising it. These errors are common in everyday communication and can easily lead to misunderstandings, unfair judgments and lost duels. 🐘

Have a great week,

Chris
themindcollection.com