What are contrary statements?

• A. Statements that are both universal, but differ in quality.
• B. Statements that are both particular, but differ in quantity.
• C. Statements that have the same truth value.
• D. Statements that are logically equivalent.

Answer: (A)

Contraries are a pair of universal statements about a class that differ in quality (one affirmative, one negative). Because they assert opposite things about all of a class, they cannot both be true at the same time. For example, All dogs are mammals and No dogs are mammals cannot both hold. They can both be false, however, if some dogs are mammals and some are not. This is what makes them a distinct relation: universal statements that differ in quality.

The other options describe different relationships: two particular statements or phrases about quantity don’t capture the universal-affirmative vs universal-negative clash; statements with the same truth value or being logically equivalent would imply a different kind of relationship entirely.