Form of a syllogism based on the Modus Ferio, in which a negative existential proposition is inferred from negative universal and affirmative existential premisses.
No M is P.
Some M are S.
Therefore, Some S are not P.
For example:
No rectangle is a circle.
Some rectangles are squares.
Therefore, Some squares are not circles.
Modus Ferison is very similar to Modus Ferio, the only difference is that the terms in the minor statement are swapped.
The name “Ferison” is a mnemonic term that helps to remember the most important characteristics of this mode: The “F” at the beginning indicates that it is related to the Modus Ferio, while the vowels indicate the types of statements used in the form: “e” and “o” stand for a negative universal and existential, the “i” for an affirmative existential statements.