====== Intensional fallacy ====== An informal [[logic:informal_fallacies:ambiguity:index|fallacy of ambi­guity]], in which terms that can refer to the same [[glossary:extension|extension]] (synonyms) are used inter­change­ably in a con­text in which they have non-iden­tical con­nota­tions because of the way and manner in which they refer to it ([[glossary:intension|inten­sions]]). For example: > The terms “morning star” and “evening star” are both used to refer to the planet Venus. > The //morning star// can be seen in the morning. > Therefore, also the //evening star// can be seen in the morning. Even though the //[[glossary:extension|extension]]// of the two terms is iden­tical (they both refer to the [[wp>Venus|planet Venus]]), they are not true syno­nyms in all as­pects, since they each each refer to it in dif­fer­ent ways (i.e. they have dif­fer­ent //[[glossary:intension|inten­sions]]//), namely that they allude to the //morning// and //evening//, res­pect­ively. In case of the "evening star", it can only reason­ably refer­red to as appear­ing in the //evening// sky. ===== Other names ===== * Illicit substitution of identicals * Intensional fallacy * [[logic:informal_fallacies:ambiguity:masked_man|“Masked man” (fallacy)]] ===== Description ===== The //intensional fallacy// belongs to the group of [[logic:informal_fallacies:ambiguity:index|fallacies of ambiguity]], but is in some sense the opposite of the other fallacies in this group, which are all based on [[glossary:equivocation:index|equivocations]]: while those are about a single expression, which is used in two or more different meanings ([[glossary:extension|extensions]]), this fallacy is base on multiple terms which appear to refer to the same extension, but with different [[glossary:intension|intensions]]. ===== More examples ===== ==== Intensions in the concept of God ==== > The pope believes in God. > The term "God" describes the same entity as "Allah". > Therefore, the pope believes in Allah. Even though Christianity, Islam and Judaism, due to their common history, indeed refer to the same deity; And even though “الله” [Allāh ], as well as “יהוה” [JHWH ] can be regarded as direct translations of "God" (and are at least in some context also used in this way), the Arabic and Hebrew terms have further //intensions//, which stand in the way of a conclusion like the above. ===== See also ===== * [[glossary:equivocation:index|Equivocation]] * [[glossary:extension|Extensions]] * [[glossary:intension|Intensions]] ===== More information ===== * [[wp>Masked-man fallacy]] on //Wikipedia// * [[https://www.logicallyfallacious.com/logicalfallacies/Illicit-Substitution-of-Identicals|Illicit Substitution of Identicals]] on //Logically Fallacious// * [[https://www.fallacyfiles.org/illisubs.html|The Masked Man Fallacy]] on //Fallacy Files//