Is Aristotle the Father of the Square of Opposition ?

International audienceIt is often said that we find the square of opposition in the Organon of Aristotle. But an historical approach of the ancient texts leads us to question the claim. In this paper, I intend to show how from the logical definition of a contradiction, Aristotle was able to set up the main points which constitute the square of opposition. Aristotle analyzed for the first time the principle relations between the opposite propositions. But did Aristotle draw the square? Through a comparison of the two Aristotelian accounts of contradiction (in the Categories and Topics first, and then in the De Interpretatione), we observe that it is the logical definition which gives birth to the square, and not the semantic account of contradiction conceived of as one of the four meanings of ‘to be opposite’. But if Aristotle is the first to conceive of the main relations of the opposite propositions in the De Interpretatione, he is not the first to draw the square. According to extant texts, the first square was designed long before by Apuleius, the second by Ammonius and the third by Boethius. We shall examine how each diagram is introduced and what are their features. The aim of this article, beyond the search for the father of the square of opposition, is to answer to the question : what is the square of opposition good for