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Title: On the Aristotelian Roots of the Modal Square of Opposition
Author(s): GEUDENS, Christophe , DEMEY, Lorenz
Journal: Logique et Analyse
Volume: 255    Date: 2021   
Pages: 313-348
DOI: 10.2143/LEA.255.0.3290193

Abstract :
The modal square of opposition is a diagram visualizing the opposition and entailment relations holding between the modalities of possibility, impossibility, necessity, and contingency. A time-honored claim in the scholarship holds that the modal square was first described by Aristotle at De int. 12-13. This paper establishes two theses: (1) the notion that the modal square is explicitly contained in De int. 12-13 is not supported by the textual evidence; (2) the modal square can be obtained from De int. 12-13 under the assumption of a contraposition law that Aristotle establishes elsewhere, at An. pr. I.46. The conclusion is that Aristotle cannot be seen as the father of the modal square, but that the square can be derived from his logic.

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