Masked man fallacy

The masked man fallacy happens when one term is replaced by another equivalent term in a context where that substitution changes meaning.

Example

“Oedipus wants to marry Jocasta.
Jocasta is Oedipus’ mother.
Therefore, Oedipus wants to marry his mother.”
(The conclusion assumes knowledge Oedipus does not have.)

Applied example (political)

“The whistleblower criticized the measure. The whistleblower is your boss. Therefore your boss criticized the measure.” (It assumes the identity is known.)

Applied example (mystical)

“You trust the anonymous guide. The anonymous guide is your neighbor. Therefore you trust your neighbor.” (Belief context changes.)

Why it is fallacious

• Logical equivalence does not preserve meaning in opaque contexts.
• It confuses names with the subject’s knowledge.
• It shifts intention without justification.

How to spot it

• A name is swapped for another “identical” one.
• Meaning depends on what the subject knows or believes.
• Psychological conclusions are drawn from formal identities.

How to respond

• Distinguish facts from beliefs.
• Ask whether the subject knows the substituted identity.
• Keep the original context without automatic replacement.