Averroes (Ibn Rushd) Logic

Origin. Ibn Rushd (1126-1198). Andalusian philosopher. Aristotle commentator. Against Avicenna on some points. Foundation of Latin Averroism.

Models. Strict Aristotelian logic. Demonstration over dialectic. Against Avicennian innovations. Commentaries as method. Scientific knowledge.

Formalism.

Three types of commentary: Short (mukhtaṣar): epitome. Middle (talkhīṣ): paraphrase with analysis. Long (sharḥ): line-by-line commentary. Progressive depth.

Against Avicenna: Reject conditional syllogistic primacy. Categorical syllogism fundamental. Propositional logic derived. Aristotelian purity.

Demonstration (burhān): Propter quid (burhān limā): from cause to effect. Quia (burhān anna): from effect to cause. Propter quid superior. Scientific knowledge.

Scientific knowledge: Must be demonstrated. From necessary premises. Through middle term as cause. Certain, not probable.

Modal syllogistic: Follow Aristotle closely. Necessity and possibility. Against Avicenna's modifications. Two-dimensional reading.

Physics and demonstration: Natural science demonstrative. Physical premises necessary. Not merely dialectical. Against skepticism.

Method: Commentary extracts Aristotle's logic. Compare with previous commentators. Critical analysis. Original contributions via exposition.

Symbols.

Term	Arabic	Gloss	Role
jawāmiʿ	جوامع	Epitome	The shortest of the three commentary levels
talkhīṣ	تلخيص	Middle commentary	Paraphrase with analysis
tafsīr	تفسير	Long commentary	Lemma-by-lemma exposition
sharḥ	شرح	Commentary	The general term for the enterprise
qiyās	قياس	Syllogism	Held to exhaust formal inference
burhān limā	برهان لم	Demonstration why	From cause to effect; the superior kind
burhān anna	برهان أن	Demonstration that	From effect to cause
muṭlaq	مطلق	Absolute, assertoric	The unmodalized premise whose reading his modal repair turns on
jadal	جدل	Dialectic	Where he places theological argument

Metatheory. Averroes worked at three levels — epitomes (jawāmiʿ), middle commentaries (talkhīṣ), and long lemma-by-lemma commentaries (tafsīr) — but of the Organon he gave the long treatment only to the Posterior Analytics, which marks where he took the difficulty to lie. His programme was to recover Aristotle against Avicenna: he rejected the primacy Avicenna had given to conditional syllogistic and Avicenna's reinterpretation of the modal premises, holding the categorical syllogism to exhaust formal inference. The hardest technical problem he inherited was Aristotle's own, the mixed modal syllogisms whose validity Aristotle asserts but cannot consistently derive; Averroes proposed reading the assertoric premise as predicating essentially, and revised the account more than once without reaching a settled version. His demarcation of demonstration from dialectic did further work: in Faṣl al-Maqāl and Tahāfut al-Tahāfut he argued that theological argument is dialectical, so Ghazālī's objections never attain demonstrative standing.

Applies to. Islamic philosophy. Medieval logic. Aristotelian tradition. History of science.

Limitations. The commitment to Aristotle constrains the theory and not merely the method. Treating the categorical syllogism as the whole of formal inference demotes conditional and disjunctive reasoning to derived status, so Avicenna's propositional developments are rejected rather than extended — one reason the Andalusian line closed while the eastern tradition went on developing. The modal syllogistic he defends is Aristotle's, and its known incoherences are met by reinterpreting the assertoric premise rather than by revising the system, a repair that leaves other moods unaccounted for and that he himself kept rewriting. Demonstration is characterized by the standing of the premises and by the middle term's being a cause, which is a condition on explanation rather than on validity, so nothing formal follows from it. And the textual base is unstable: several commentaries survive only in Hebrew or Latin, the Arabic lost.