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Modus Ferio

A form of syllogism in which a new negative existential proposition is derived from a negative universal and an affirmative existential proposition.

No M is P.
Some S are M.

Some S are not P.

For example:

No square is a circle.
Some rectangles are squares.

Some rectangles are not circles.

Name

The name “Ferio” is an artificial word describing the inference scheme: The “e” and “i” stand for a negative and positive universal quantifications, respectively, and the “o” for the negative existential quantification in the conclusion..

For more information on this naming scheme, and on syllogisms in general, see the article on syllogisms in the glossary.

Variants

The following forms are the variants of Modus Ferioand can all be transformed back to it:

See also

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Ad Hominem Info is a project to explain and categorize the most common systematic fallacies and fallacies. On this page, you will find a background article that briefly explains an important logical concept, which may be needed to better understand another article in this area.
For more information, please see the main category “logic

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