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WorkAl-Ghazali

The Standard of Knowledge

A handbook of Aristotle's logic in Arabic, written to decode the vocabulary of the *Incoherence* and to make jurists test their arguments.

by Al-Ghazali293 passages held

  • Arabic, the original language
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Original title
معيار العلم في فن المنطق
Original language
Arabic

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Overview

Two motives stand at the head of this handbook of logic, and its author names both. The broad one is that logic does for reasoning what prosody does for verse and grammar for correct Arabic: without it nobody can tell a sound proof from a broken one, in law or theology any more than in philosophy. The narrow one is The Incoherence of the Philosophers, finished in January 1095, in which al-Ghazālī had argued with the falāsifa, the followers of Aristotle, in their own technical language; this book explains that language. It sets out the logic the philosophers had learned from Avicenna (Ibn Sīnā), the Persian philosopher: words and what they signify, how propositions combine into syllogisms, how a definition is made. A final book sorts their terms for the kinds of things that exist. The theologians are in it too. In one passage an objector asks how anyone can be certain that a man whose neck is cut will die, when the theologians teach that God creates the death at the moment of the cutting and not through it; the answer is that no sane person doubts the death, and the deeper question is left to the Incoherence. Its last lines point to a companion volume, and The Criterion of Action opens by saying that the standard for knowledge is done and the standard for action comes next. With al-Ghazālī, Aristotle's logic in Avicenna's version made its lasting entry into the religious sciences. He kept it there: late in life he set a summary of logic at the front of al-Mustaṣfā, his handbook on the principles of Islamic law, completed in 1109.

Key concepts

What is the difference between conception and assent?

They are the two things any inquiry can be after. Conception is grasping what something is, and it is reached by a definition or a description. Assent is judging that something is true, and it is reached by an argument, such as a syllogism or an induction. The whole book is organised around this pair: half of it teaches how to define well, the other half how to prove well.

What is a syllogism?

A syllogism is an argument in which two premises sharing a middle term force a conclusion. The book’s own example: every intoxicant is wine, all wine is forbidden, so every intoxicant is forbidden. “Wine” is the middle term. If the premises are true and the form is right, the conclusion cannot be false. The book teaches the valid forms so that readers can check any argument, legal or theological, against them.

What are genus and differentia?

Genus and differentia are the two parts of a proper definition. The genus says what general kind a thing belongs to, and the differentia says what sets it apart within that kind: drink is a genus, and intoxicating is what marks off one kind of drink. Features that pick a thing out without saying what it is, such as neighing for a horse, make descriptions, not definitions.

Why is induction not a proof?

Induction reasons from inspected cases to a general rule. The book warns that if only some cases are inspected, an unexamined exception may exist, so the rule is only probable. Even a complete survey gives probability rather than certain knowledge of a universal rule. For legal judgments, it says, probability is enough; for a demonstration about God or the world, it is not.

What is the “reason” of a legal ruling?

In legal analogy, the reason of a ruling is the feature of the original case on which the ruling actually rests, and which justifies carrying it to a new case. Intoxication is the reason wine is forbidden, because it damages the mind. Two cases may look alike in name or appearance and still differ in the one feature that matters, so the jurist must say what the reason is and show that it is the right one.

Themes of the book

What this book returns to, gathered into themes and ordered by how much of the text each one occupies.

A Scale for Arguments

How can anyone tell a sound proof from a convincing mistake? The book offers a test that applies to theology, law and philosophy alike, and ranks the starting points of every argument by how far they can be trusted.

Logic, the opening says, does for reasoning what prosody does for verse and grammar for speech: without it a broken argument can pass for a proof. The book then ranks the premises an argument can start from, from first truths and things seen, through repeated experience and widely reported facts, down to opinions people merely share and judgments of imagination that feel certain and are false. Experience earns its place through a hidden inference, that what recurs so regularly cannot be chance. A conclusion is only as strong as its weakest premise.

  • logic
  • syllogism
  • demonstration
  • certainty
  • inference
  • fallacies
  • probability
  • induction
  • perception
  • imagination
  • reason

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Saying What a Thing Is

What separates what a thing is from what merely happens to be true of it? Much of the book teaches how to define, because a dispute over a badly defined word cannot be settled.

Before arguing about anything, the book insists, one must know what one's words mean and what the thing is. It separates a feature without which a thing cannot even be understood from features that merely happen to belong to it, and builds definitions from the first kind: a general class narrowed by what sets this kind apart, as intoxicating marks one kind of drink. Its final book sorts everything that exists into substance and the kinds of qualities and relations, the vocabulary the philosophers used and the theologians needed to read them.

  • definition
  • essence
  • universals
  • predication
  • language
  • semantics
  • categories
  • classification
  • substance
  • relations
  • necessity

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Law Reasoned Like Logic

Can reasoning about the law be as rigorous as reasoning about nature? The book applies the philosophers' logic to the jurists' analogies and asks when a ruling may be carried from one case to another.

Al-Ghazālī wrote for jurists as much as for philosophers, and his examples come from the law: intoxicants, forbidden sales, the dates that may not be sold fresh because they shrink when dried. Legal and rational inquiry, he argues, share one structure and differ mainly in their premises. A legal analogy is valid only when the shared feature really is the reason for the ruling, so the jurist must say what that reason is and defend it. Familiar opinion is no substitute: people are to be judged by the truth, not the truth by people.

  • legal reasoning
  • legal analogy
  • jurisprudence
  • causation
  • knowledge
  • epistemology

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Within this work

passages held
293
distinct concepts
272
by passages held, corpus-wide
#252

What this book thinks together

The wheel takes this book’s leading concepts and shows how often they come up together. The wider the band between two, the more of its passages speak of both. Among them, most often together: “logic” and “syllogism”.
Concept co-occurrence, strongest first 8 concepts, joined by 22 pairings. 85 pairings reach beyond these concepts and are not drawn.
ConceptPaired conceptShared passages
logicsyllogism25
definitionessence22
definitionlogic18
demonstrationlogic14
epistemologylogic10
definitiondemonstration8
essencelogic8
causationlogic6
causationdefinition5
demonstrationepistemology5
essenceuniversals5
causationsyllogism4
demonstrationsyllogism4
epistemologysyllogism4
causationdemonstration3
definitionuniversals3
demonstrationessence3
epistemologyuniversals3
logicuniversals2
causationessence1
definitionepistemology1
demonstrationuniversals1

Works held

The author's work in order, this book marked in place. Your-language title first, the original beneath it where the two differ; side chips show which full texts are held.

  1. Deliverance from Error (المنقذ من الضلال)

    An intellectual autobiography, written at Nishapur after his return to teaching in 1106; Claud Field's Confessions of Al Ghazzali first brought it into English in 1909.

     EN
  2. The Alchemy of Happiness (Kīmiyā-yi Saʿādat)

    His major work in Persian, written around 1105 for readers without Arabic, and a shorter companion to the Revival of the Religious Sciences.

     EN
  3. The Incoherence of the Philosophers (تهافت الفلاسفة)

    The book by which he is known in philosophy, finished in Baghdad in January 1095, months before he gave up his chair there and left the city.

     AR
  4. The Just Balance (القسطاس المستقيم)

    One of several answers to the Ismāʿīlīs, this one cast as a dialogue on the road; his autobiography points readers to it instead of repeating its case.

     AR
  5. The Marvels of the Heart (كتاب شرح عجائب القلب)

    The twenty-first of the forty books of the Revival of the Religious Sciences, and the ground for the books on vices and virtues that follow it.

     AR
  6. The Niche of Lights (مشكاة الأنوار)

    Among his late works, and the one in which his thought comes closest to the mystics: three chapters on a single verse of the Qurʾān and a single saying of the Prophet.

     AR
  7. The Standard of Knowledge (معيار العلم في فن المنطق) you are here AR
  8. مقاصد الفلاسفة

    A report before a refutation: Avicenna's system set out without a word of objection, then framed by a short preface and ending that point ahead to The Incoherence of the Philosophers.

     AR
  9. ميزان العمل

    The second half of a pair: having set a standard for knowing in The Standard of Knowledge, he set one here for acting, still in Baghdad, around 1095.

     AR
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