3 - Arabic Logic after Avicenna

Summary

When the North African historian Ibn Khaldūn (d. 1406) reflected on the development of logic, he distinguished – along with a number of other fourteenth-century observers – between “the early” and “the later” logicians (Rosenthal 1958, III, 143). The former included those who took their point of departure from the classical Organon, such as the philosophers al-Fārābī (d. 950), Avicenna (d. 1037) and Averroes (d. 1198). The first of “the later logicians”, according to Ibn Khaldūn, were the Persians Fakhr al-Dīn al-Rāzī (d. 1210) and Afḍal al-Dīn al-Khūnajī (d. 1248). These disregarded the Categories entirely and gave short shrift to the “matter” of the syllogism: demonstration, dialectic, sophistical fallacies, rhetoric, and poetics. Instead, they focused almost exclusively on the five predicables, definition and description, propositions and their immediate implications (such as conversion, contraposition) and the formal syllogism. By Ibn Khaldūn's time, “the later logicians” had carried the day. “Logic” (manṭiq) had ceased to be a discipline in which one comments upon or paraphrases or summarizes the books of the Organon; it had become rather a field dealing with the acquisition of concepts (taṣawwurāt) through definition or description and the acquisition of assents (taṣdīqāt) through syllogism. Ibn Khaldūn himself lamented this development, but the resulting narrower view of the scope of manṭiq made it much closer to the contemporary understanding of “logic” than the earlier Peripatetic conception of it as a discipline that covers all the books of the Organon.

The roots of the new view of the scope of “logic” can be said to go back to Avicenna himself, especially to his condensed presentation of logic in al-Ishārāt. But Ibn Khaldūn was not guilty simply of oversight. Avicenna had followed the books of the Organon in his magnum opus al-Shifā’: Categories, On Interpretation, Prior Analytics, Posterior Analytics, Topics, Sophistical Refutations, Rhetoric, and Poetics. His student Bahmanyār (d. 1065) similarly divided the logic part of his philosophical summa al-Taḥṣīl into chapters covering Eisagoge, Categories, On Interpretation, Prior Analytics, and Posterior Analytics. The powerful influence of Avicenna's Ishārāt was due in large part to its widely discussed commentary by Fakhr al-Dīn al-Rāzī.