====== Affirmative conclusion from a negative premise ======

Incorrect application of a [[glossary:syllogism|syllogism]] by deriving an affirmative (positive) conclusion from a negative premise.

For example<span no-print> [[app>#AE1A|Open in Syllogism-Finder App]]</span>:

> All <var>squares</var> are <var>rectangles</var>.
> No <var>circles</var> are <var>squares</var>.
> <span conclusio><s invalid "Affirmative conclusion from a negative premise">Therefore, All <var>circles</var> are <var>rectangles</var>.</s></span>

===== Description =====

One fundamental rule for all syllogistic and similar inferences is that if //one// of the premises is a negative, the conclusion can only also be a negative statement. There are no valid syllogism forms that contradict this rule. Trying to construct one is a [[logic:formal_fallacies:index|formal fallacy]].

Furthermore, if //both// premises are negative, no conclusion can be inferred at all (<span maniculus "see:">[[logic:formal_fallacies:exclusive_premises|Fallacy of exclusive premises]]</span>).

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

  * [[logic:formal_fallacies:exclusive_premises|Fallacy of exclusive premises]] – when //both// premisses are negative.
  * [[logic:formal_fallacies:negative_conclusion_from_affirmative_premises|Negative conclusion from affirmative premises]] – Reversal of this form of fallacy.
  * [[glossary:syllogism|Syllogism]] – underlying form of inference.

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

  * [[wp>Affirmative conclusion from a negative premise]] on //Wikipedia// 
  * [[https://www.logicallyfallacious.com/tools/lp/Bo/LogicalFallacies/12/Affirmative-Conclusion-from-a-Negative-Premise|Affirmative Conclusion from a Negative Premise]] on //Logically Fallacious//