== Undistributed middle ==
====== (Fallacy of the) undistributed middle [term] ======
Describes an (invalid) [[glossary:syllogism|syllogism]], in which the //middle term// that is connecting the two premises is not used according to the rules of [[glossary:distribution|distribution]].
Example of a syllogism [[app>#IA1A|Show in Syllogism-Finder App]] with an //undistributed middle//:
> Some animals are cats.
> All dogs are animals.
> Therefore, all dogs are cats.
===== Other names =====
* Non distributivi [sed collectivi ] medii
===== Rules of distribution =====
The distribution rules for syllogisms are summarized in the article on [[glossary:distribution|distribution]]. The specific rule that is violated by this fallacy can be formulated as follows:
The //middle term//, which connects the two premises, must occur in a distributed position in //at least one// of the premises.
The following table gives an overview of the distribution of the terms in the four [[glossary:categorical_statement|categorical statement types]]:
^ Type ^ Statement ^ Subject ^ Predicate ^
^ A | All S are P
| distributed | not distributed |
^ E | No S is P
| distributed | distributed |
^ I | Some S are P
| not distributed | not distributed |
^ O | Some S are not P
| not distributed | distributed |
With regards to the example above, the premises therein are of the types **I** and **A**; The //middle term// ("animals") appears in both cases in //undistributed// positions, therefore this form of a //syllogism// is not valid.
===== See also =====
* [[glossary:distribution|Distribution]]
* [[glossary:syllogism|Syllogism]]
===== Weitere Informationen =====
* [[wp>Fallacy of the undistributed middle]] on //Wikipedia//
* [[https://www.logicallyfallacious.com/tools/lp/Bo/LogicalFallacies/87/Fallacy-of-the-Undistributed-Middle|Fallacy of (the) Undistributed Middle]] on //Logically Fallacious//
* [[http://www.fallacyfiles.org/undismid.html|Undistributed Middle Term]] on //Fallacy Files//