A universal affirmative of the form “Every S is P” converts to a particular affirmative: “Some P are S.”
Every horse is an animal → Some animals are horses.
Every rose is a flower → Some flowers are roses.
In the traditional system, the subject class is assumed to have members; in modern logic the existential assumption has to be stated.
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Rule for universal affirmatives
Simple Conversion of Propositions: Definition, Method and Rules
A universal affirmative of the form “Every S is P” converts to a particular affirmative: “Some P are S.”
Every horse is an animal → Some animals are horses.
Every rose is a flower → Some flowers are roses.
In the traditional system, the subject class is assumed to have members; in modern logic the existential assumption has to be stated.