Modal Propositions: The Eight Simple Modalities

1. A proposition qualified by modality

The last lesson distinguished subject, predicate, assertion and the location of negation. The next question is how the predicate belongs, or fails to belong, to the subject: necessarily, permanently, while some description applies, or at a specified time.

“Humans are animals” and “Humans are necessarily animals” share the same subject and predicate. The second explicitly qualifies the predicative relation with necessity.

Such a qualification is a modality (jihah), and a proposition expressing one is a modal proposition (qaḍiyyah muwajjahah). Modality is not quantity: quantity concerns how many instances, whereas modality concerns the mode of the judgment.

2. Matter, modality and its expression

The matter of a proposition (māddah) is the actual character of the subject–predicate relation, such as its being necessary, possible or impossible. Its modality (jihah) is the character conceived or asserted in the judgment; words expressing it convey that modality.

For instance, “A human is an animal” has a necessary subject–predicate relation even when the speaker does not pronounce “necessarily.” Conversely, adding “necessarily” to a false statement cannot make its subject matter necessary.

Thus the expressed qualification and the reality of the relation are distinct aspects. Analysis of a modal statement should attend to both without confusing them.

3. The source division: fifteen modalities

«والموجهات خمسة عشر: ثمانية منها بسيطة، وسبعة منها مركبة»
There are fifteen modalities: eight are simple and seven are compound.

A simple modality states a fundamental mode of judgment within this classification. A compound modality joins modal qualifications in an affirmative or negative construction.

This lesson takes the eight simple forms: unrestricted necessary, unrestricted permanent, generally conditional, generally customary, time-specific, time-indefinite, generally absolute and generally possible. The seven compound forms belong to the subsequent discussion.

4. The organizing questions behind the eight forms

The eight forms differ along two connected dimensions: the force of the claim and the period or condition for which it holds.

Necessity: the contrary cannot obtain under the stated qualification.
Permanence: the relation continues throughout the specified period; permanence alone does not automatically establish necessity.
Description: a condition linked to the subject's descriptive title is maintained.
Time: necessity is attached to a specified or unspecified time.
Actuality and possibility: one may assert actual occurrence or deny the necessity of its opposite.

The most serious confusions are inferring “necessary” from “has happened,” or “actual” from “possible.”

5. 1 — Unrestricted necessity

«الضرورية المطلقة»
Unrestricted necessary proposition.

Here affirmation or denial of the predicate is necessary for as long as the subject itself exists. The operative qualification is:
«ما دام ذات الموضوع موجودة»
As long as the subject itself exists.

“Unrestricted” means this necessity is not tied to an additional descriptive title or an appointed time. It is still qualified by the existence of the subject. For example, being an animal necessarily belongs to a human throughout that human's existence.

6. Affirmative and negative necessary cases

«الإنسان حيوان بالضرورة»
A human is necessarily an animal.

This is an affirmative necessary proposition. Animality is contained in the concept of humanity; a human cannot, while human, fail to be an animal.

«والإنسان ليس بحجر بالضرورة»
And a human is necessarily not a stone.

This is a negative necessary proposition. As long as the human exists, being a stone is necessarily denied. Necessity is therefore compatible with both affirmation and negation.

7. 2 — Unrestricted permanence

«الدائمة المطلقة»
Unrestricted permanent proposition.

The judgment continues throughout the existence of the subject: as long as that subject exists, the predication remains in force. The expression bi-l-dawām marks continuing truth; bi-l-ḍarūrah marks necessity.

Their temporal scope may look alike, but their logical force differs. Permanence concerns continuing predication, whereas necessity concerns the impossibility of the contrary under the stated qualification. A relation's persisting is not, by itself, proof of its necessity.

8. The book’s example of permanence

«كل فلك متحرك بالدوام»
Every celestial sphere is perpetually moving.

Within the older cosmological framework used by the book, this illustrates an affirmative permanent proposition. The text also supplies a permanent denial of rest to that sphere. Logically the example links predication to the whole duration of the subject's existence.

The old celestial-sphere model should not be presented as a verified claim of modern physics. For understanding the logical form, the essential point is that “permanently” means continuous predication, not automatically “necessarily.”

9. Necessity versus permanence

Necessity says the contrary cannot obtain under the given qualification. Permanence says the predicate in fact holds throughout the stated period.

Suppose a particular lamp remained lit throughout its short life. “It stayed lit its whole lifetime” reports continuity, but being lit did not belong to the lamp's essence; it could have been extinguished. In contrast, “A human is an animal” expresses a necessary genus–species relation.

Thus, even if two claims mention the same span of time, they need not express the same modality. Continuity and necessity demand different analyses.

10. 3 — General conditional necessity

«المشروطة العامة»
General conditional necessary proposition.

Affirmation or denial is necessary while the subject retains the description expressed in its title. The source's condition is:
«ما دام ذات الموضوع موصوفا بالوصف العنواني»
For as long as the subject itself is described by its titular attribute.

When the subject is “writer,” the judgment concerns the person while writing, rather than merely while that person exists. This distinguishes the generally conditional modality from unrestricted necessity, which is tied to the existence of the subject as such.

11. The writer example under the descriptive condition

«كل كاتب متحرك الأصابع بالضرورة ما دام كاتبا»
Every person writing is necessarily moving their fingers so long as they are writing.

The example concerns handwriting, with writer considered in the active condition of writing. Once the act ceases, the qualification underlying this particular necessity no longer obtains.

Effect of the condition: the person may continue to exist although the descriptive state ends. It would therefore be incorrect to infer “their fingers must always be moving.” The judgment applies only while writing.

12. 4 — General customary permanence

«العرفية العامة»
General customary permanent proposition.

This form expresses permanence during the time in which the subject has its titular description; necessity is not the direct qualification asserted. Its temporal condition resembles that of general conditional necessity: the subject must retain the named description.

«بالدوام كل كاتب متحرك الأصابع ما دام كاتبا»
Permanently, every writer moves their fingers as long as they are writing.

The example shows that “while writing” can appear in both forms, although bi-l-ḍarūrah and bi-l-dawām express different logical forces.

13. Conditional and customary: same scope, different force

These two forms are close because both are qualified by the subject's titular description, yet their logical force differs.

General conditional: the relation is necessary while that description holds.
General customary: the relation is permanent while that description holds.

Suppose a “teacher” is considered precisely while teaching. “While teaching, the person continually speaks” may be a claim about continuity, but it does not thereby express logical necessity; one may teach by writing or gestures.

The key is to separate the duration of a condition from the force of the predication.

14. The title-description versus the subject itself

The commentary identifies the titular description as the property by which a subject is designated. Such a title may indicate a species, a genus or differentia, or a property external to the subject's essence.

Examples:
“Human”: humanity refers to the subject's species-character.
“Writer”: writing is a capacity or activity; the person may remain after that activity stops.
“White”: removal of whiteness does not necessarily destroy the object.

When a judgment says “while described as such,” one must identify which description sets the scope. Otherwise changing the subject's title can quietly change the claimed modality.

15. 5 — Time-specific necessity

«الوقتية المطلقة»
Unrestricted time-specific modality.

This asserts necessity of affirmation or denial at a specified time within the subject's existence. Its defining feature is that the time or relevant occasion is definite, such as a stated physical configuration.

Unrestricted necessity concerns the subject throughout its existence, whereas this form limits necessity to an identified time. The judgment's ceasing outside that time does not by itself falsify the time-qualified proposition.

16. Source example: the time of a lunar eclipse

«كل قمر منخسف بالضرورة وقت حيلولة الأرض بينه وبين الشمس»
Every moon is necessarily eclipsed when Earth intervenes between it and the Sun.

The textbook specifies the occasion when Earth lies between Sun and Moon, treating the eclipse relation as necessary in that arrangement.

The logical lesson is the time qualification: the claim does not assert that the Moon is eclipsed throughout its existence. It applies to the stated occasion. Confusing the time-specific mode with unrestricted permanence would erase that essential limitation.

17. 6 — Necessity at an unspecified time

«المنتشرة المطلقة»
Unrestricted necessity at an unspecified time.

The proposition makes affirmation or denial necessary at some unspecified time during the subject's existence. “Unspecified” does not mean no time exists; rather, the judgment does not name which time.

«كل حيوان متنفس بالضرورة وقتا ما»
Every animal is necessarily breathing at some time.

This is the textbook's general example. The key formal point is waqtan mā, “at some time,” not an empirical assertion that all animal species breathe by the same biological mechanism.

18. A definite time versus an unspecified time

Time-specific: necessity holds at an identified time.
Time-indefinite: necessity holds at some time not identified.

For example:
“When fuel burns in this engine, heat is produced at that occasion” specifies a qualifying occasion.
“At some point while the vehicle runs, heat is produced” does not say exactly when.

These illustrative claims clarify temporal specification; whether a real physical judgment is strictly necessary requires separate justification. Changing specified to unspecified does not itself alter the force of necessity.

19. 7 — General absolute modality

«المطلقة العامة»
General absolute modality.

This form asserts the predicate's actual obtaining or not obtaining for the subject without necessarily requiring a qualification of necessity, permanence, or a special descriptive condition. The source describes its temporal openness as «في أحد الأزمنة الثلاثة»
In one of the three times.

The word bi-l-fiʿl emphasizes actuality here: a relation is asserted to obtain, rather than to be necessary or perpetual. “It actually occurs” is not equivalent to “it could not have been otherwise.”

20. Affirmation and denial under actuality

«كل إنسان ضاحك بالفعل»
Every human is actually laughing, in the example’s stated sense.

The text also supplies a negative counterpart. These illustrate the technical role of bi-l-fiʿl; opposite formulations are not to be accepted as simultaneously true of the same subject in the same respect and at the same time.

“This door is open now” is an assertion about actuality. It does not establish that the door was always open, will always remain open, or had to be open. One must not import necessity or permanence into a generally absolute judgment merely because it affirms or denies something.

21. 8 — General possibility

«الممكنة العامة»
General possibility.

This mode denies the necessity of the opposite side. In an affirmative case, it denies that the negation must hold; in a negative case, it denies that the affirmation must hold. It is therefore not identical with “both sides are equally possible.”

«كل نار حارة بالإمكان العام»
Every fire is hot in the sense of general possibility.

For this affirmative example, the relevant claim is that the absence of heat is not necessary. General possibility cannot be defined simply as the fact that the predicate is actually present.

22. General possibility in negative propositions

«ولا شيء من النار ببارد بالإمكان العام»
And no fire is cold, in the sense of general possibility.

In the negative form, what is denied is the necessity of the corresponding affirmation. This does not mean every possible negative statement is always actually true. First identify the proposition's quantity and quality; then interpret the general possibility qualifying that negative judgment.

Affirmative general possibility: the negation is not necessary.
Negative general possibility: the affirmation is not necessary.

The “opposite side” is always relative to the affirmative or negative quality of the current proposition.

23. Why general possibility includes necessary truths

“A human is an animal” is necessary; its opposite, “A human is not an animal,” is certainly not necessary. Thus the affirmation also satisfies the denial of necessity of its opposite. In that broad sense, general possibility can encompass a necessary affirmative claim.

It can also include a contingent predication, such as the possible acquisition of writing ability by a particular person.

Therefore general possibility entails only that the opposite judgment is not necessary. It does not by itself establish that the present judgment actually obtains, fails to obtain, or is equally balanced with its opposite.

24. The first four: scope and force

For the first four modalities, ask how long the judgment applies and with what force.

1. Unrestricted necessary: necessity while the subject exists.
2. Unrestricted permanent: permanence while the subject exists.
3. Generally conditional: necessity while the titular description holds.
4. Generally customary: permanence while the titular description holds.

Two axes therefore combine:
Existence of the subject / retention of its descriptive title.
Necessity / permanence.

Attending only to duration, or only to the words “necessary” and “permanent,” can lead to confusing these forms.

25. The last four: time, actuality and possibility

5. Time-specific: the relation is necessary at a specified time in the subject's life.
6. Time-indefinite: it is necessary at some unspecified time.
7. Generally absolute: the predicate actually obtains or does not obtain, without requiring necessity or permanence.
8. Generally possible: the opposite judgment is not necessary.

Time-specific and time-indefinite forms both involve necessity but differ in specification of time. The generally absolute form concerns actuality; the generally possible form concerns non-necessity of the opposite.

Always identify the proposition before classifying its modality; they are related but different questions.

26. Worked classification of new propositions

Case 1: “Every triangle necessarily has three sides so long as it is a triangle” expresses a necessary relation tied to the nature of a triangle.
Case 2: “A person writing by hand moves their fingers while writing” is restricted by a descriptive title; if necessity during that activity is intended and supported, it has the generally conditional form.
Case 3: “The Moon is eclipsed at this stated occasion” mentions a specified time; strict time-specific necessity also needs the necessity of that relation to be stated or supported.
Case 4: “This student is standing now” reports actuality, not necessarily permanence or necessity.

For each expression, establish subject, predicate, temporal/descriptive restriction and modal force before assigning its technical class.

27. Review and the transition to compound modalities

Modality qualifies the subject–predicate relation. The eight simple modes are unrestricted necessary, unrestricted permanent, generally conditional, generally customary, time-specific, time-indefinite, generally absolute and generally possible.

When examining a modal proposition, ask three questions in sequence:
1. Is it affirmative or negative, and of what subject?
2. Is its scope tied to the subject's existence, a descriptive title, a time, or merely actuality?
3. Is its force necessity, permanence, actuality, or possibility by denying necessity of the opposite?

Mastery of these eight forms prepares for the seven compound modalities, in which modal qualifications are combined.