Illicit minor is a

formal fallacy In philosophy, a formal fallacy, deductive fallacy, logical fallacy or non sequitur (; Latin for " tdoes not follow") is a pattern of reasoning rendered invalid by a flaw in its logical structure that can neatly be expressed in a standard logic sy ...

committed in a categorical syllogism that is invalid because its minor term is undistributed in the minor premise but distributed in the conclusion. This fallacy has the following

argument form In logic, logical form of a statement is a precisely-specified semantic version of that statement in a formal system. Informally, the logical form attempts to formalize a possibly ambiguous statement into a statement with a precise, unambigu ...

: :All A are B. :All A are C. :Therefore, all C are B. ''Example:'' : All cats are felines. : All cats are mammals. : Therefore, all mammals are felines. The minor term here is mammal, which is not distributed in the minor premise "All cats are mammals", because this premise is only defining a property of possibly some mammals (i.e., that they're

cat The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members of ...

s.) However, in the conclusion "All mammals are felines", mammal ''is'' distributed (it is talking about all mammals being felines). It is shown to be false by any mammal that is not a

feline Feline may refer to: Zoology * Loosely, Felidae, a member of the cat family, which includes the subfamilies Pantherinae and Felinae (conventionally designated a felid) ** Following the taxonomic convention, Felinae, the subfamily of Felidae that ...

; for example, a dog. ''Example:'' : Pie is good. : Pie is unhealthy. : Thus, all good things are unhealthy.

See also