The Development of Per Impossibile from Aristotle to Quṭb al-Din Razi

Aristotle took Per Impossibile as a form of Hypothetical Syllogism which was composed of a Syllogistic and a non-syllogistic part. But he didn’t express the relation between these two parts clearly. Alexander of Aphrodisias and Philoponus didn’t add any specific comments to Aristotle’s view. Al-Farabi believed that Per Impossible includes three deductions: two categorical syllogisms and one exceptional syllogism; Avicenna introduced Connective Conditional Syllogism, and, based on it, he explained the relation between two parts that Aristotle propounded in Per Impossible. This interpretation is accepted by many of Islamic logicians, nevertheless Averroes followed Aristotle’s outline and ruled out Avicenna’s Connective Conditional Syllogism. Afḍal al-Din Maraqi took Aristotle’s opinion and clarified the relation between Syllogistic and non-syllogistic parts well, finally Quṭb al-Din Razi modified some aspects of Avicenna’s view.