Skip to content
Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

contraposition

Swapping subject and predicate and replacing both with their complements.

Contraposition of a categorical statement switches the subject and predicate terms and replaces each with its complement. It gives an equivalent statement for A and O statements, but not for E or I statements.

Examples

  • "All cats are mammals" contraposes to "All non-mammals are non-cats."

See also

conversion obversion complement of a class contrapositive
Read the full section →