Categorical Logic·Concept·Lesson 2 of 6

The Square of Opposition and Existential Import

Introduces the square of opposition, explains the relationships of contradiction, contrariety, subcontrariety, and subalternation among A, E, I, and O propositions, and distinguishes the traditional and modern treatments of existential import.

← Categorical Propositions and the A, E, I, O Forms Categorical Logic: Terms, Classes, and Syllogistic Form Venn Diagrams for Categorical Propositions →

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In this lesson · 7 sections · 5 worked examples · 4 practice activities

Four propositions, four relationships
Contradiction is the safest inference
Contrariety: the top of the square
Subcontrariety and subalternation in the traditional reading
…and 3 more

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