Al-Ghazālī's Logic

Origin. Al-Ghazālī (1058-1111). Logic without metaphysics. Miʿyār al-ʿilm (Standard of Knowledge). Logic as neutral tool. Foundation of post-classical Islamic logic.

Models. Logic separable from philosophy. Neutral methodology. Compatible with theology. Against philosophers' metaphysics. Logic for jurisprudence.

Formalism.

Logic as tool: Logic = scale (mīzān). Weighs arguments. No metaphysical commitment. Neutral instrument.

Separation thesis: Logic ≠ philosophy. Greek metaphysics separable. Muslims can use logic. Against wholesale rejection.

Syllogistic: Standard Aristotelian syllogism. Four figures. Valid moods. No innovation here.

Definition: Essential definition: genus + differentia. Descriptive definition: accidents. Real definition preferred. Understand essence.

Jurisprudential application: Qiyās (analogical reasoning in law). Logical qiyās relates. Legal reasoning structured. Logic serves fiqh.

Critique of philosophers: Tahāfut al-Falāsifa. Philosophers exceed logic. Their metaphysics not demonstrated. Logic doesn't prove eternity of world.

Demonstrative vs dialectical: Philosophers claim demonstration. Actually dialectic at best. Premises not certain. Over-confidence critiqued.

Symbols.

Term	Arabic	Gloss	Role
mīzān	ميزان	Balance, scale	His image for logic: it weighs arguments and asserts nothing
qisṭās	قسطاس	Correct balance	Title term of the work presenting the figures as Qurʾānic scales
miʿyār	معيار	Standard	Title term of his main logical work
taṣawwur	تصور	Conception	Grasping a meaning; served by definition
taṣdīq	تصديق	Assent	Judging it so; served by syllogism
ḥadd	حد	Definition	Genus plus differentia, giving the essence
qiyās	قياس	Syllogism, analogy	Logical syllogism and legal analogy share the word
burhān	برهان	Demonstration	The standard he holds the philosophers to and finds them failing
jadal	جدل	Dialectic	What he says their metaphysics amounts to
tahāfut	تهافت	Incoherence	Title term of the critique

Metatheory. Ghazālī's contribution is not a logical result but a reclassification with consequences. In the fourth introduction to the Tahāfut al-Falāsifa he insists that logic carries no metaphysical content — nothing in it bears on the eternity of the world or the nature of the soul — so that rejecting the philosophers' doctrines gives no ground for rejecting their instrument. He then turned the instrument on them, arguing that their metaphysical proofs fail the demonstrative standard they had set for themselves and are dialectical at best. He carried the point into law: al-Mustaṣfā opens with a logical prologue and the declaration that whoever does not master logic cannot be relied upon in any science, and al-Qisṭās al-Mustaqīm presents the syllogistic figures as scales already present in the Qurʾān. The Avicennan division of knowledge into conception and assent, definition serving one and syllogism the other, passes through him to become the standard frame of later Arabic logic.

Applies to. Islamic philosophy. Logic and theology. Legal reasoning. History of logic.

Limitations. The neutrality thesis is asserted rather than shown, and it is not obviously true of the logic he transmits: essential definition by genus and differentia presupposes real essences, and the demonstrative ideal requires middle terms to be causes, both substantive commitments of the philosophy from which logic is being separated. His logical content is Avicennan and unoriginal — no new rules, no new results, no analysis Avicenna had not given — which is why Maqāṣid al-Falāsifa, circulating in Latin without its framing preface, was read as straightforward Avicennism and its author taken for a follower of the philosophers. The critique in the Tahāfut is targeted rather than general: it shows that particular proofs fail, not that demonstration cannot reach metaphysical conclusions. And the alignment of Qurʾānic arguments with the syllogistic figures is exegesis, not a result about the figures.