What is the First Law of Opposition?

• A. Contrary statements cannot both be true at the same time, but they can both be false at the same time.
• B. Contradictory statements cannot both be true or both be false at the same time.
• C. Subcontraries cannot both be true but can both be false.
• D. Subalterns cannot be both true or false.

Answer: (B)

The idea tested is how contraries relate. Contraries are a pair of statements about the same subject with opposite quality, typically a universal affirmative and a universal negative (for example, “All S are P” and “No S are P”). They cannot both be true at the same time because if every S is P, none can be outside that, and if none are P, none can be inside that either. But they can both be false if there are some S that are P and some S that are not P. That is precisely the behavior described: contraries cannot both be true, but can both be false. The other relational patterns—contradictories, subcontraries, and subalterns—do not describe this same pair, which is why this option is the best fit.