Categorical Propositions

Every categorical proposition has two properties that determine its logical form:

1.) quality- every standard form categorical proposition has a quality (affirmative or negative).  If the proposition affirms class inclusion (logical subject is completely or partially included in the logical predicate), then the proposition is affirmative. On the other hand, if the proposition denies that the logical subject (completely or partially) is included in the logical predicate then the proposition is negative. Thus, E and O propositions are negative in quality. A and I are affirmative.

2.) quantity- every standard form categorical proposition has a quantity (universal or particular). If the logical subject term refers to all members of the class named by the logical subject term, the quantity is universal. Thus A and E are universal propositions. If the logical subject only refers to some members of the class designed by the logical subject term, then the proposition is particular. O and I are particular.

   3.) Distribution of subject and predicate terms in a categorical proposition - We interpreting the subject terms and predicate terms of categorical propositions to refer to classes or to designate classes of objects. And the claim asserted or denied by a proposition is about class inclusion and class exclusion of the class designed by the subject term in or not in the class designed by the predicate term.  The subject and predicate term may designate all members of a class or only some members of a class. Thus, a proposition distributes a term if the term in the proposition refers to all members of the class designated by that term. If the term only refers to some members but not all members of the class, the term is undistributed.

All ( Distributed) are (Undistributed).
No (Distributed) are (Distributed).
           Some (Undistributed) are (Undistributed).
Some (Undistributed) are not (Distributed).

Propositions as classes . (Robinson's power-point presentation)