

Definition:
A categorical proposition is a proposition which relates two classes to each other
(through a direct assertion of agreement or disagreement between them), both of which
are delineated with a categorical term. There are only four forms of a categorical
proposition:
All S are P.
No S are P.
Some S are P.
Some S are not P.
The first, All S are P, is a universal affirmative. The second, No S are P, is a universal negative. The third, Some S are P, is a particular affirmative. The fourth, Some S are not P, is a particular negative.
The classes are represented by the letters, S and P. The categorical terms are the quantifiers: All, No, Some.
Categorical propositions are usually divided up into four groups: A, E, I and O:
A: All S are P (One category is a subset of another)
E: No S are P (The two categories do not intersect)
I: Some S is/are P (The two categories intersect)
O: Some S is/are not P (One category is not a subset of another)
A key issue is the nature of distribution. A category is said to be distributed if the proposition refers to every member of the category. The first term is distributed in A propositions; the second is distributed in O propositions; both are distributed in E propositions; and none are distributed in I propositions.
One distinguishing feature of categorical propositions is quantity:
 Universal propositions (A, E) refer to all members of the class designated by its subject term.
 Particular propositions (I, O) refer just to some members of the class designated by its subject term.
Another distinguishing feature of categorical propositions is quality:
 Affirmative propositions (A, I) express a relationship of inclusion between members of the classes designated by its terms.
 Negative propositions (E, O) express a relationship of exclusion between members of the classes designated by its terms.
Also Known As: none
Alternate Spellings: none
Common Misspellings: none
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