Form of a syllogism based on the Modus Ferio, in which a negative existential proposition is inferred from each negative and affirmative universal premisses. This form has an additional existential requirement.
No P is M.
All M are S.
[and there exists at least one M]*
Therefore, Some S are not P.
No circle is a square.
All squares are rectangles.
[and there exists at least one square]*
Therefore, Some rectangles are not circles.
The name “Fesapo” 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 “a” stand for a negative and affirmative universal premisses and the “o” for a negative existential conclusion.