Which type of opposition consists of two universal statements differing in quality?

• A. Contrary statements
• B. Subcontrary statements
• C. Subalternate statements
• D. Contradictory statements

Answer: (A)

This question tests contraries: two universal statements that differ in quality. For example, “All S are P” and “No S are P” share the same subject and predicate but one is affirmative and the other negative. Because they go to opposite ends of the universal spectrum, they cannot both be true at the same time; if all S are P, there aren’t any S that are not P, and if no S are P, there aren’t any S that are P. Yet they can both be false if some S are P and some S are not P.

Other forms of opposition don’t fit two universals differing in quality. Subcontraries involve particular statements (some S are P vs some S are not P) and can both be true or both be false. Subalternation links a universal to its particular of the same quality, not two universals. Contradictories pair a universal with a particular of opposite quality, so they cross quantity and quality rather than remain two universals.