====== Fallacy of exclusive premises ======

A [[glossary:syllogism|syllogism]] with of //two negative premises// has no valid conclusion.

For example<span no-print> [[app>l#EE2E|Open in Syllogism-Finder App]]</span>:

> No <var>polygon</var> is a <var>circle</var>.
> No <var>rectangle</var> is a <var>circle</var>.
> <span conclusio><s invalid "Fallacy of exclusive premises">Therefore, no <var>rectangle</var> is a <var>polygon</var>.</s></span>

===== Description =====

Negative statements have much less descriptive power than positive ones – we learn less about ''<var>A</var>'' from the statement "<var>A</var> is not a tree" than from the statement "<var>A</var> is a house". Therefore, there are a number of restrictions on what can be done with negative statements.

Even with only a single negative premise, it is no longer possible to draw any //positive// conclusion (<span maniculus "see:">[[logic:formal_fallacies:affirmative_conclusion_from_negative_premise|affirmative conclusion from a negative premise]]</span>).

If both premises are negative, there are no ways in which the //middle term// can reliably connect the statements. Therefore, it is not possible to infer a conclusion which connects the major and minor terms. In other words: it is not possible to draw a conclusion.

===== See also =====

  * [[logic:formal_fallacies:affirmative_conclusion_from_negative_premise|Affirmative conclusion from a negative premise]] – even a single negative premise means no affirmative conclusion can be drawn
  * [[logic:formal_fallacies:negative_conclusion_from_affirmative_premises|Negative conclusion from affirmative premises]] – only affirmative premisses don’t allow a negative conclusion
  * [[glossary:syllogism|Syllogism]] – underlying form of inference.

===== More information =====

  * [[wp>Fallacy of exclusive premises]] on //Wikipedia//
  * [[https://www.logicallyfallacious.com/tools/lp/Bo/LogicalFallacies/82/Exclusive-Premises|Exclusive Premises]] on //Logically Fallacious//
  * [[http://www.fallacyfiles.org/exclprem.html|Exclusive Premisses]] on //Fallacy Files//
  * [[http://philosophy.lander.edu/logic/exclusive_fall.html|Syllogistic Fallacies: Exclusive Premisses]] on the servers of //Lander University//