## Square of Opposition

Classical logicians described the various logical relations among the four standard forms in terms of what they called the square of opposition, and identified four relations among the four standard forms when placed in the square of opposition:

Contraries

Comprehension Questions

 1. In which relationship from the square of opposition is it true that both propositions cannot be true and both cannot be false? a) contradictory b) contrary c) subcontrary d) subalternation 2. In which relationship from the square of opposition is it true that both propositions cannot be false, but they can both be true? a) contradictory b) contrary c) subcontrary d) subalternation 3. In which relationship from the square of opposition is it true that both propositions cannot be true, but they can both be false? a) contradictory b) contrary c) subcontrary d) subalternation 4. In which relationship from the square of opposition is it true that when the universal is true the particular one of the same quality is true and when the particular is false the universal one of the same quality is false? a) contradictory b) contrary c) subcontrary d) subalternation 5. Which propositions in the square of opposition are contradictories? a) A and I b) A and E c) I and O d) A and O e) E and O 6. Which propositions in the square of opposition are subalternates? a) A and I b) A and E c) I and O d) A and O e) E and I 7. Which propositions in the square of opposition are contradictories? a) A and I b) A and E c) I and O d) E and I e) E and O 8. Which propositions in the square of opposition are subalternates? a) A and E b) I and O c) A and O d) E and I e) E and O

Existential Import

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