Logic and Ontology in Khūnajī and His Successors

• Applicant: Behnam Zolghadr, Ph.D.
• Subject Area: History of Philosophy ; Theoretical Philosophy
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 456690998

This project deals with logic and ontology in the works of Afḍal al-dīn al-Khūnajī (d. 1248) and some of his successors. Khūnajī is known as the second greatest Arabic logician after Avicenna. Like medieval European logicians, Arabic logicians built upon the logic of Aristotle, but with many innovations. Avicenna’s significant reworking of Aristotelian logic became the standard model until Khūnajī, who undertook a major departure from Avicenna’s logic and influenced many logicians after him. While many studies have been devoted to early Arabic logic and especially Avicenna, studies on Khūnajī’s logic and in general logic in the Islamic world after 1200 A.D. are still scarce. The proposed research would remedy this lack by studying Khūnajī’s logic, its ontological implications and the influence of Khūnajī on later Arabic logicians. Among Khūnajī’s innovations were his new account of propositional analysis and novel categorization of propositions based on their existential import. He also gave an extensive account of logical relations between propositions, as well as new logical rules for the connectives (negation, disjunction and conditionals). The upshot is that Khūnajī’s notion of logical consequence is different from that of Avicenna: some inferences are valid for Khūnajī which were invalid in Avicena’s logic, and vice versa. The result of this research will be an exposition of Khūnajī’s logic and a reconstruction of his system using the formal machinery of contemporary logic. A further aim of the project is to examine the ontological consequences of this system: particularly far-reaching implications are associated with his distinction between propositions in terms of the existential status of their subject matter. Moreover, Khūnajī advocates the validity of inferences from impossible premises; again, this has ontological implications, in this case concerning impossible objects. It also commits him to a paraconsistent notion of logical consequence. Both as a resource for understanding Khūnajī’s own ideas and to determine what further departures were made from his logic in the following generations, this project will also explore several later thinkers who responded to Khūnajī. These will include especially Najm al-Dīn al-Kātibī (d. 1276), whose Šamsīyya became an important teaching text, and the commentaries devoted to it, especially that by Quṭb al-Dīn al-Rāzī al-Taḥtānī (d. 1365), which itself received many glosses and super glosses.

• DFG Programme: Research Grants