Single Idea 15879

[catalogued under 4. Formal Logic / A. Syllogistic Logic / 2. Syllogistic Logic]

Full Idea

Square of Opposition: 'all A are B' and 'no A are B' are contraries; 'some A are B' and 'some A are not B' are sub-contraries; the pairs 'all A are B'/'some A are B' and 'no A are B'/'some A are B' are contradictories.

Gist of Idea

The Square of Opposition has two contradictory pairs, one contrary pair, and one sub-contrary pair

Source

Rom Harré (Laws of Nature [1993], 3)

Book Reference

Harré,Rom: 'Laws of Nature' [Duckworth 1993], p.62


A Reaction

[the reader may construct his own diagram from this description!] The contraries are at the extremes of contradiction, but the sub-contraries are actual compatible. You could add possible worlds to this picture.

Related Idea

Idea 9405 Square of Opposition: not both true, or not both false; one-way implication; opposite truth-values [Aristotle]