The Five Predicables: Differentia, Property, Common Accident, Essential and Accidental Attributes

1. From species to differentia

We have studied genus and species, including the highest genera. A further question remains: what makes species within one genus different in their intrinsic natures?

A human and a horse both fall under 'animal'. That genus expresses a shared nature but does not identify what makes the human species distinct within it.

The essential universal that provides this distinction is differentia (fasl). Property and common accident will then complete the five predicables.

2. The source definition of differentia

فصل: الثالث: الفصل، وهو كلي مقول على الشيء في جواب «أي شيء هو في ذاته؟»
The third predicable is differentia: a universal predicated in answer to 'What kind of thing is it in its essence?'

Differentia is an essential determination that distinguishes a species from other species under the same genus. Rational (nāṭiq) serves as the differentia of the human species. It indicates rational capacity, not merely audible speech.

3. The two questions asked about a thing

'Mā huwa?' asks what a thing is: an answer can express its complete essence ('rational animal') or a constituent such as its genus ('animal').

'Ayyu shayʾin huwa fī dhātihī?' seeks the feature by which that thing is intrinsically distinguished within its genus. The answer for the human species is 'rational'.

'Animal' is shared by humans and horses; 'rational' supplies the species-forming difference. Genus and differentia are both intrinsic, but they perform different explanatory roles.

4. Why differentia is intrinsic

An attribute is not a species' differentia if removing it leaves the specified nature intact. Black hair or currently walking does not constitute humanity.

In the classical definition, rational identifies an intrinsic constituent of what the human species is. Without that determination, its account within the genus remains incomplete.

This does not claim that each human is constantly reasoning. A differentia concerns what a species is, not an activity observed at a given moment. This matters when comparing it with properties and accidents.

5. Proximate differentia

Differentiae are classified as proximate and remote. A proximate differentia distinguishes a species from others within its proximate genus.

'Rational' is proximate for the human species because 'animal' is its proximate genus, and rationality marks its species-level distinction within animals.

Here 'proximate' refers to a position in the essential hierarchy, not to practical importance or everyday familiarity.

6. Remote differentia

A remote differentia distinguishes a species at the level of a more remote genus but does not yet provide its final distinction within the proximate genus.

'Sentient' (ḥassās) is remote with respect to the human species: humans and other animals are sentient, so this feature separates them from some other growing bodies, but not from horses.

Rational — proximate for human
Sentient — remote for human
The distinction depends on the level in the genus–species hierarchy.

7. Worked comparison of near and far differentiae

Consider the sequence:
Body → growing body → animal → human

'Animal' is the proximate genus of human. 'Rational' marks the human species off from other animals, making it proximate. 'Growing body' is a more remote level; being sentient marks a distinction at that earlier stage.

'Sentient' cannot be the proximate differentia of human because other animals are sentient too. It does not distinguish the human species within its nearest genus.

8. Differentia as constitutive

وللفصل نسبة إلى النوع، فيسمى مقوما؛ لدخوله في قوام النوع وحقيقته.
In relation to a species, differentia is called constitutive because it enters into the species' constitution and essence.

Rational is constitutive (muqawwim) of human. It is a defining element in the classical analysis of the species, not an accidental event that happens to particular humans.

9. Differentia as dividing a genus

ونسبة إلى الجنس فيسمى مقسما.
In relation to the genus, differentia is called divisive because it divides the genus into distinguishable groups.

Relative to the genus 'animal', 'rational' is divisive (muqassim): it marks rational animals off from non-rational animals.

The same differentia is constitutive of the species and divisive of the genus. These labels describe two different relations, not two different properties.

10. One differentia, two logical roles

For the same feature, distinguish the relation involved:
Relative to human: rational is constitutive, because it contributes to the species' essence.
Relative to animal: rational is divisive, because it separates rational from non-rational animals.

It would be incomplete to call it only constitutive and deny its divisive role. Ask 'relative to what?' The classification changes with the genus or species being considered, not because the feature itself has changed.

11. What constitutes higher and lower natures

كل مقوم للعالي مقوم للسافل، كالقابل للأبعاد؛ فإنه مقوم للجسم النامي والحيوان والإنسان.
Every constitutive feature of a higher nature also constitutes its lower kinds. For example, receptivity to dimensions constitutes body and continues through growing body, animal and human.

Because a human is a kind of body, the essential constituents of body remain within the analysis of human nature. The logical inclusion runs from higher genus to subordinate species.

12. Why the corresponding converse fails

وليس كل مقسم للعالي مقسما للسافل.
Not every feature that divides a higher genus divides each of its lower species.

'Sentient' can divide a wider class of growing bodies into animals and non-animals. It does not then divide animals into sentient and non-sentient animals: in this classical account all animals are sentient.

Inheritance of a constitutive feature down a hierarchy does not imply repeated subdivision by that same feature at every subordinate level.

13. Definition of property (khassah)

الكلي الرابع الخاصة، وهو كلي خارج عن حقيقة الأفراد، محمول على أفراد واقعة تحت حقيقة واحدة فقط، كالضاحك للإنسان والكاتب له.
The fourth predicable is property: a universal external to the essence of individuals but predicable only of individuals under one species, such as the capacity to laugh or write in relation to humans.

Two conditions matter:
1. The feature is not a constituent of the species' essence.
2. It belongs peculiarly to that specified species.

'External' here means outside the definition of essence, not unrelated to the subject.

14. Potential ability versus current activity

The source's 'laughing' example does not require every person to be laughing at every moment. It refers to a capacity for laughter. The 'writer' example likewise concerns a capacity rather than writing at this instant.

Actually laughing now is not permanent in each person. In the classical example, capable of laughter is treated as a property of the human species.

Distinguishing potential capacity from present action prevents mistaking silence or sleep for counterexamples.

15. The decisive difference between property and differentia

Both 'rational' and 'capable of laughter' characterize the human species, but their logical status differs.

Rational — differentia: an intrinsic defining constituent.
Capable of laughter — property: peculiar to the species but outside its definition of essence.

'Laughing animal' can identify the species by a special mark, but it is not an essential definition in the way 'rational animal' is. This prepares the later distinction between essential definition and description.

16. Definition of common accident

فصل: الخامس من الكليات العرض العام، وهو الكلي الخارج المقول على أفراد حقيقة واحدة وعلى غيرها، كالماشي المحمول على أفراد الإنسان والفرس.
The fifth predicable is common accident: an extrinsic universal predicated of individuals of one species and also of individuals of another, such as 'walking' applied to humans and horses.

Walking does not constitute the essence of either species and is not exclusive to the human species. Both externality to essence and applicability beyond one species are required.

17. Property versus common accident

Property and common accident are both extrinsic to essence. Their distinction lies in the range of subjects to which the universal applies.

Property: a capacity peculiar to one species, such as the classical human example of laughter.
Common accident: a characteristic found across species, such as walking in humans and horses.

Observing a feature in one individual does not establish its logical class. Ask whether it is essential and, if not, whether it is exclusive to one species.

18. All five predicables together

أن الكليات خمس، الأول: الجنس، والثاني: النوع، والثالث: الفصل، والرابع: الخاصة، والخامس: العرض العام.
Note: the predicables are five: genus, species, differentia, property and common accident.

Genus: shared nature across species — animal.
Species: one specific nature shared by its individuals — human.
Differentia: essential distinction — rational.
Property: extrinsic but peculiar to one species — capacity for laughter.
Common accident: extrinsic and shared across species — walking.

19. Intrinsic and extrinsic predicables

فاعلم أن الثلاثة الأول يقال لها: الذاتيات، ويقال للآخرين: العرضيات.
Know that the first three are called intrinsic predicables, and the remaining two extrinsic predicables.

Intrinsic: genus, species and differentia, all associated with an essential account (with a technical qualification about species).
Extrinsic: property and common accident, neither of which constitutes the species' essence. This distinction later underlies essential definitions and descriptions.

20. A terminological qualification about species

وقد يختص اسم الذاتي بالجنس والفصل فقط، ولا يطلق على النوع بهذا الإطلاق لفظ الذاتي.
Sometimes 'intrinsic' is reserved for genus and differentia only, and under this narrower usage it is not applied to species.

The reason is that genus and differentia are constituents of the specific essence, whereas species expresses that essence as a whole rather than as a single constituent.

The broader classification of three intrinsic predicables and the narrower usage of two are compatible once the differing scope of the term is recognized.

21. How accidents relate to essence

In this technical discussion, extrinsic or accidental does not simply mean short-lived, random or quickly disappearing. It means not a constituent of the essence.

An extrinsic feature may necessarily accompany its subject and still remain outside the definition of what it is. Conversely, an essential differentia does not become accidental merely because a particular activity is not being exercised.

This leads to the distinction between necessary and separable accidents.

22. A two-stage method of classification

To classify a universal characteristic, proceed in two stages.

Stage 1: Does it belong to the essence? If so, identify the relevant intrinsic relation: genus, species or differentia.
Stage 2: If it is outside the essence, is it peculiar to one species? If yes, it is a property; if shared across species, a common accident.

Application:
Animal — genus of human.
Rational — differentia of human.
Capable of laughter — property of human.
Walking — common accident relative to human.

One subject can receive predicates of quite different logical kinds.

23. Necessary accident

العرضي - أعني الخاصة والعرض العام - ينقسم إلى لازم ومفارق.
The extrinsic predicables—property and common accident—are divided into necessary and separable accidents.

A necessary accident (lāzim) cannot be separated from its subject under the relevant consideration.

For example, being even necessarily belongs to the number four. Evenness is not the defining meaning of 'four', but the number four cannot fail to be even.

24. Necessity of essence versus existence

When examining necessity, ask whether a feature is inseparable from the subject's essence or from some specified condition of its external existence.

Essentially necessary: four's evenness. Four cannot remain four while becoming odd.
Necessary relative to existence: a trait may be inseparable under a given condition of a subject's actual existence without entering the definition of its essence.

The source distinguishes these types of necessity. Most importantly, a feature's being necessary does not automatically make it a defining constituent.

25. Immediate or narrower obvious implication

الأول: ما يلزم تصوره من تصور الملزوم كالبصر للعمى.
The first kind is where conceiving the subject entails conceiving the correlate, as the concept of sight is required in understanding blindness.

Blindness is understood as a privation of sight, so grasping blindness necessarily involves the meaning of sight.

This is the narrower sense of an evident concomitant: the very concept of the subject brings the related concept to mind without first combining two separately grasped meanings in an additional judgment.

26. Broader obvious implication

والثاني: ما يلزم من تصور الملزوم واللازم الجزم باللزوم، كالزوجية للأربعة.
The second kind is one in which conceiving both subject and concomitant produces an immediate judgment of necessary connection, as evenness does for four.

First grasp four, then evenness—divisibility into two equal whole-number parts. Four divides into 2 and 2, so their connection is self-evident.

This is the broader sense of evident necessity. The emphasis is the immediate assent to the relation once both concepts are understood.

27. Separable accident

والعرض المفارق: ما لم يمتنع انفكاكه عن الملزوم، كالكتابة بالفعل للإنسان، والمشي بالفعل له.
A separable accident is one that can cease to belong to its subject, as in a human actually writing or actually walking.

A person may stop writing or sit down and still remain human. These actions are states that can be absent without destroying the subject's nature.

Actual writing and actual walking are therefore separable accidents, unlike the defining differentia 'rational' or the necessary evenness of four.

28. Durable and changing separable accidents

فصل: العرض المفارق - أعني ما يمكن انفكاكه عن المعروض - أيضا قسمان:
Separable accident—an accident capable of separating from its subject—is divided into two kinds: one persists with its subject under relevant external circumstances; the other ceases, either quickly or slowly.

Quickly ceasing: a moving object's motion comes to an end.
Slowly changing: some bodily characteristics alter between youth and old age.

An accident's persisting for a long period is not the same as its being logically inseparable. The key distinction remains whether separation is possible.

29. Synthesis: from predicables to definitions

At the end of the five predicables, three decisions should be clear:
1. Inside or outside essence? Genus, species and differentia belong to the intrinsic account; property and common accident are extrinsic.
2. If extrinsic, peculiar or shared? A property is peculiar to one species; a common accident applies across species.
3. If accidental, separable or inseparable? An inseparable feature is necessary; a separable one can cease to apply.

'Human is a rational animal' gives an essential account. 'Human is capable of laughter' identifies by a property. This distinction prepares the next discussion of definition, essential definition and description.