A predicate is a term affirmed or denied of a subject in a categorical or a simple modal proposition. Subject and predicate compose a sort of matter, which the copula, asserting agreement or variance between them, forms into the proposition. An individual term can be a predicate only if the subject also is individual. Other terms, whether concrete or abstract, positive or negative, are not so restricted. Since to be without an attribute is a kind of attribute, no distinction is made here between positive and negative terms.
Predication is the assertion that an attribute (signified by the predicate) does or does not characterize something (signified by the subject). There are thus two kinds of predication: affirmative, asserting such characterization; and negative, denying it. Consideration of the objective status of what the terms signify discloses that both affirmative and negative predication can be of two sorts, identical and disparate. Predication is identical when the attribute the predicate signifies does in fact characterize every referent of the subject; it is disparate when this attribute does not characterize any, or fails to characterize some, referent of the subject. Both of these can be either formal or material. The identical is formal when the predicate is the genus, difference, or property of the subject. Formal disparity results from incompatibility between what the predicate signifies and an attribute the subject signifies. When the subject neither entails nor excludes the predicate, the identity or disparity actually present is material.
Traditional logic teaches that an affirmative proposition is true if and only if its predication is identical, and that a necessary proposition is true if and only if such identical predication is formal. The truth and falsity of negative propositions are not determined by identity or disparity of predication.
See Also: predicables.
[j. j. doyle]