Suhrawardi’s Debt to Avicenna in his Syllogistic

Suhrawari’s syllogistic is based upon the three reductions: (1) the reduction of the negative propositions to positive ones by obversion, (2) the reduction of the particular propositions to universal ones by exposition, and (3) the reduction of the contingent and impossible propositions to necessary ones by definite necessity. Thus, the four moods of the first figure may be reduced to one mood, the four moods of the second figure may be reduced to another one, and the six moods of the third figure may be reduced to a third mood. from these three moods, the first is self-evident in its validity. But Suhrawardi proves the validity of the other two moods by two illuminationistic rules. I will show in this article that Suhrawardi is indebted to Avicenna in all these respects. Obversion is borrowed from Avicenna’s al-Mukhtasar al-Awsat; exposition is an Aristotelian method which Avicenna applies in all of his logical works; the definite necessity and one of the two illuminationistic rules are adopted from his al-Shifa’: Kitab al-Qiyas; and the other illuminationistic rule is extracted from his al-Najat. So Ziai and Walbridge’s opinion that Suhrawardi’s Syllogistic is a sharp divergence from Avicenna’s Syllogistic will be wrong.