What are contradictory statements?

• A. Statements that differ in both quality and quantity.
• B. Statements that have the same quality and quantity.
• C. Statements that have opposite truth values but same quantity.
• D. Statements that are both universal and particular.

Answer: (A)

Contradictory statements are pairs of propositions whose truth values are always opposite, so one must be true exactly when the other is false. They differ in both quality and quantity: a universal form contrasts with a particular form, and an affirmative form contrasts with a negative form. For example, “All swans are white” and “Some swans are not white” cannot share the same truth value; if the first is true, the second must be false, and vice versa. Likewise, “No swans are white” and “Some swans are white” are also contradictories.

That’s why the best description is statements that differ in both quality and quantity. The other options describe relationships where the differences are only in one aspect or mix categories that don’t capture the opposite-truth-value relationship true of contradictions.