Definition and Its Four Forms: Complete/Incomplete Essential and Descriptive Definitions

1. From the five predicables to definition

The earlier discussion distinguished genus, species, differentia, property and common accident. These distinctions now become useful in the practical task of defining a thing so that its meaning can be understood.

For example, the terms “animal,” “rational,” and “capable of laughter” may feature in an account of the human. But they play different roles: animal is genus, rational is differentia, and being capable of laughter is a property.

The choice and combination of these predicables determines the kind of definition.

2. The textbook definition of a definiens

«معرف الشيء ما يحمل عليه لإفادة تصوره»
A thing's definiens is what is predicated of it to bring about its conception.

The definiens is the expression that explains; the definiendum is the thing or concept being explained. In “A human is a rational animal,” “human” is the definiendum and “rational animal” the definiens.

The definition uses predication not to deliver an unrelated fact but to make the subject intelligible.

3. The aim is to make a concept understood

The primary aim of a definition is to make a meaning understood, not merely to supply an additional fact about an existing object. If someone seeks the essential account of “human,” “rational animal” answers the relevant question.

“A human is in the market” supplies information about a person; it does not define the human species.
“A human is a rational animal” places the human within a genus and states the distinguishing feature.

A defining statement may resemble an ordinary proposition in form, but it has a different instructional purpose.

4. The four kinds of definition

«وهو على أربعة أقسام»
And it has four kinds.

1. Complete essential definition (hadd tamm): proximate genus and proximate differentia.
2. Incomplete essential definition (hadd naqis): remote genus with proximate differentia, or the proximate differentia alone.
3. Complete descriptive definition (rasm tamm): proximate genus and a property.
4. Incomplete descriptive definition (rasm naqis): remote genus with a property, or the property alone.

Essential definitions rely on essential constituents; descriptions identify by a distinguishing property.

5. Proximate and remote genus

The proximate genus is the immediately relevant genus above a species. For the human species, “animal” is the proximate genus.

A remote genus stands higher in the hierarchy. “Body” is more remote than “animal” because it includes many things other than animals.

Comparison:
Human ← animal: proximate genus
Human ← body: remote genus

Whether the definition uses the proximate or remote genus is essential to its classification as complete or incomplete.

6. What the proximate differentia identifies

The proximate differentia expresses the essential feature by which one species is distinguished from other species sharing its proximate genus. Traditional logic uses nāṭiq (“rational”) for the human species.

In this technical usage, nāṭiq does not merely mean speaking aloud; it refers to the intellectual capacity characteristic of humans. Someone who cannot speak is still human.

“Animal” identifies the wider class; “rational” gives the specific essential distinction. Their combination forms the complete essential definition.

7. The source rule for complete essential definition

«فالتعريف إن كان بالجنس القريب والفصل القريب يسمى حداً تاماً»
If a definition uses the proximate genus and proximate differentia, it is called a complete essential definition.

Example: الإنسان حيوان ناطق
The human is a rational animal.

“Animal” is the proximate genus; “rational” is the proximate differentia. Together they identify both the encompassing essential class and what differentiates this species within it.

It is complete because the two appropriate essential components are present.

8. How a complete essential definition conveys essence

A complete essential definition does more than place the definiendum in a class: it states the feature that essentially separates the species from other members of that class.

“Human is an animal” names a genus but does not distinguish humans from horses, goats, and other animals.

“Human is a rational animal” adds the appropriate differentia, thereby distinguishing the species.

The proximate genus alone is not enough for hadd tamm; the proximate differentia must accompany it.

9. The source rule for incomplete essential definition

«وإن كان بالجنس البعيد والفصل القريب أو به وحده يسمى حداً ناقصاً»
If it uses the remote genus with the proximate differentia, or the proximate differentia alone, it is called an incomplete essential definition.

Example 1: الإنسان جسم ناطق
The human is a rational body.
Example 2: الإنسان ناطق
The human is rational.

In both cases the essential distinction is conveyed, but the full pair required for a complete essential definition is absent. The first uses a remote genus; the second does not mention a genus.

10. Two ways an essential definition can be incomplete

The two forms of incomplete essential definition do not supply exactly the same amount of information, although both share the same classification.

“Rational body” provides a remote genus and the proximate differentia, but omits the proximate genus “animal.”
“Rational” provides only the differentia and does not name any genus.

Incomplete does not mean false or useless. It means that the structure required for the complete essential definition has not been fully supplied.

11. The fundamental difference between hadd and rasm

An essential definition (hadd) draws on intrinsic constituents, especially differentia. A descriptive definition (rasm) uses a property connected to the species but outside its essence.

“Human is a rational animal” uses the differentia “rational” and gives an essential definition.
“Human is an animal capable of laughter” uses a property and gives a descriptive definition.

Both contain “animal.” Their difference lies in the logical status of the final feature, not in the number of words.

12. The role of a property in definition

A property (khāṣṣah) is an extrinsic attribute peculiar to a species without being an essential constituent. In the traditional example, the capacity for laughter is taken as a property of humans.

A property helps distinguish the definiendum from other species, but does not provide the same essential account as a differentia.

It is important to distinguish a capacity for laughter from actually laughing at a given moment. A sleeping or sorrowful human does not cease to be human.

13. The source rule for complete descriptive definition

«وإن كان بالجنس القريب والخاصة يسمى رسماً تاماً»
If the definition uses the proximate genus and a property, it is called a complete descriptive definition.

Example: الإنسان حيوان ضاحك
The human is an animal capable of laughter.

“Animal” is the proximate genus and “capable of laughter” is a property. The genus situates the species in its class and the property gives a distinctive mark.

It is descriptive because it uses a property rather than an essential differentia, and complete because it includes the proximate genus.

14. Why a complete description is not a complete essential definition

“Human is an animal capable of laughter” contains the same proximate genus as the complete essential definition. But the capacity for laughter is classified as a property, not the proximate differentia.

Comparison:
Hadd tamm: animal + rational (proximate differentia)
Rasm tamm: animal + capable of laughter (property)

A complete description can successfully identify the species; identifying it by a distinctive feature is not the same as explaining its intrinsic essence.

15. The source rule for incomplete descriptive definition

«وإن كان بالجنس البعيد والخاصة أو بالخاصة وحدها يسمى رسماً ناقصاً»
If the definition uses the remote genus with a property, or the property alone, it is called an incomplete descriptive definition.

Example 1: الإنسان جسم ضاحك
The human is a body capable of laughter.
Example 2: الإنسان ضاحك
The human is capable of laughter.

Both use a property as the distinguishing feature, so both are descriptive. The first uses a remote genus; the second omits a genus, so both are incomplete.

16. Compare all four definitions

The distinction becomes clearer when all four forms are applied to the same definiendum, “human.”

Complete hadd: animal + rational — proximate genus + proximate differentia.
Incomplete hadd: body + rational, or rational alone — remote genus plus differentia, or differentia alone.
Complete rasm: animal + capable of laughter — proximate genus + property.
Incomplete rasm: body + capable of laughter, or property alone.

First ask whether the identifying feature is a differentia or a property. Then ask whether the proximate genus is present. These two questions classify the definition.

17. Why a common accident cannot define a species

«ولا دخل للعرض العام في التعريفات لأنه لا يفيد التميز»
A common accident has no place in these definitions because it does not distinguish the thing.

A common accident can be shared by different species. For example, being able to walk is not peculiar to humans; many other animals walk.

Calling a human simply “something that walks” therefore fails to pick out the human species. The required distinguishing function of definition is not achieved.

18. Distinguishing a shared trait from a property

A familiar or striking attribute is not automatically a technical property. The key question is whether it is peculiar to the species or shared by others.

“Human is a body” covers many different kinds of things and does not identify the species.
“Human is something that walks” describes several animal species and fails to distinguish humans.
“Human is capable of laughter,” in the traditional logical scheme, uses a distinctive property.

This is why rasm employs a property rather than an indiscriminately shared accident.

19. Why an overly broad definition fails

A definition is expected to identify the intended definiendum. If the expression is so broad that it includes many other species, it does not adequately exclude what is outside the target.

For example, “Human is an animal” is true as a generic classification, but animal also applies to horses and numerous other species.

Naming a genus can be useful introductory information. It is not, by itself, the complete definition. An essential differentia or a distinguishing property supplies the missing discrimination.

20. Why an overly narrow definition fails

Conversely, an added condition may be too narrow and exclude genuine members of the species. Such an account fails to cover all the intended instances.

For example, defining a human as “a rational animal who can write” is defective: many humans cannot write, yet remain human.

A definition must not import a restriction that is not necessary for membership in the target kind. It should express the essence or appropriate identifying feature, not an incidental qualification.

21. Real definition and verbal definition

«التعريف قد يكون حقيقياً كما ذكرنا، وقد يكون لفظياً»
Definition may be real, as already discussed, or it may be verbal.

A real definition aims to convey what the thing is or how it is properly identified, rather than merely replace one word with another. The four forms of hadd and rasm belong to that discussion.

A verbal definition instead explains the meaning of an expression. An unfamiliar word is clarified by a more familiar or more intelligible one.

22. The source rule for verbal definition

«وهو ما يقصد به تفسير مدلول اللفظ»
It is that by which the meaning signified by a word is explained.

Suppose a learner does not know the Arabic word “ghaḍanfar.” The clarification is:
«الغضنفر الأسد»
Ghaḍanfar means lion.

The unfamiliar expression is now understood.

This, however, has not identified the lion's proximate genus and differentia. Explaining a word's meaning and providing an essential definition of the thing are distinct aims.

23. The source example of sa‘dānah

«سعدانة نبت»
Sa‘dānah is a plant.

This brief statement helps someone unfamiliar with the term “sa‘dānah” recognize the broad kind of thing it denotes. “Plant,” however, is not a complete essential definition, since it applies to numerous different species.

The purpose is preliminary verbal clarification. It should not be confused with a complete hadd, which would need the proper proximate genus and differentia.

24. Knowing a word versus knowing a thing

Learning a synonym for a word and learning what a thing essentially is are different achievements.

“Ghaḍanfar = asad” tells us that two Arabic words denote the lion. This is verbal clarification.
“Human = rational animal” is not just a synonym substitution; it uses genus and differentia to provide an essential account.

The decisive question is whether the statement explains an expression or explains the thing's essence or distinguishing character.

25. Applying the classification rules

Classify the following accounts of the human by examining their logical constituents.

1. Rational animal — complete hadd: proximate genus + proximate differentia.
2. Rational body — incomplete hadd: remote genus + proximate differentia.
3. Animal capable of laughter — complete rasm: proximate genus + property.
4. Capable of laughter — incomplete rasm: property alone.
5. Body — not an adequate discriminating example of the four: it is too broad.

Word count does not decide the classification. The logical role of each component does.

26. Correcting common errors

Error 1: “Complete” simply means long and “incomplete” means short. Correction: completeness depends on the appropriate genus and differentia/property, not length.

Error 2: Every distinctive attribute is a differentia. Correction: a differentia is intrinsic; a property can be extrinsic yet peculiar to the species.

Error 3: A common accident can define a species. Correction: because it can apply to several species, it fails the test of discrimination.

Error 4: Replacing a word with a synonym is always a complete essential definition. Correction: this usually clarifies language rather than analyzing essence.

27. Synthesis and transition to propositions

The central principle is that the kind of definition depends on the logical status of its constituent terms.

Complete hadd: proximate genus + proximate differentia.
Incomplete hadd: remote genus + proximate differentia, or differentia alone.
Complete rasm: proximate genus + property.
Incomplete rasm: remote genus + property, or property alone.

A common accident does not provide the required distinction. Real definition explains the thing, while verbal definition clarifies the expression.

The textbook next opens its second major chapter on propositions, including categorical and conditional forms. The focus shifts from explaining concepts to the structure of judgment.