What does opposition refer to in categorical logic?

• A. to be opposites; to affirm and deny the same predicate of the same subject
• B. to have the same subject and different predicates
• C. to be mutually exclusive in time
• D. to be logically equivalent

Answer: (B)

Opposition in categorical logic describes how two categorical propositions relate to each other when they talk about the same thing—specifically, they share both the same subject term and the same predicate term. This setup lets us compare what is claimed about all of the subjects with what is claimed about none of the subjects, or about some of the subjects, in a structured way.

In the classic square of opposition, two universal propositions with the same terms (All S are P and No S are P) are contraries: they cannot both be true, though they can both be false. Two particular propositions with the same terms (Some S are P and Some S are not P) are subcontraries: they cannot both be false, though they can both be true. There are also related relations like subalternation and contraposition that preserve the same subject and predicate terms when analyzing truth-transfer and equivalence.

So, the essential point is that opposition depends on keeping the same subject and the same predicate across the paired propositions; changing the predicate would move you outside the established oppositional relations.