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Modus Datisi

Form of a syllogism based on the Modus Darii, in which an affirmative existential proposition is inferred from affirmative existential and universal premisses.

All M are P.
Some M are S.

Some S are P.

For example:

All rectangles are polygons.
Some rectangles are squares.

Some polygons are squares.

Modus Datisi is very similar to Modus Darii, the only difference being that the terms in the minor statement are reversed.


The name “Datisi” is a mnemonic term that helps to remember the most important characteristics of this mode: The “D” at the beginning indicates that it is related to the Modus Darii, the “a” and the two “i” indicate the affirmative universal and existential statements that make up this form.

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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