Remaining Semantic Fallacies: Mental Concepts, Similarity, and Famous Paradoxes

1. Mistaking a mental consideration for an external thing

ومنها: أخذ الاعتبارات الذهنية والمحمولات العقلية أموراً عينية
Another fallacy is treating mental considerations and logical predicates as external, concrete properties.

Some predicates arise when the intellect considers a concept rather than when it observes a property of a physical object. The concept “human” can apply to many individuals, so it is universal. But universality does not become a physical component of each human being.

The fallacy confuses mental existence—conceiving and predicating—with external existence—things and effects outside the mind.

2. Universality qualifies a concept

فإن الكلية إنما تعرض الأشياء في الذهن دون الخارج
Universality attaches to things in the mind, not as a physical attribute outside it.

The concept “human” may be predicated of Zayd, Amr, and countless others; the intellect therefore calls the concept universal. Zayd himself remains a particular individual.

Thus “human is universal” does not say that universality is an additional physical ingredient in each person. Its subject is the concept of human as considered intellectually, not an individual's bodily composition.

3. What is meant by “the impossible exists”?

الممتنع موجود
“The impossible exists.”

Read without qualification, this sounds as if an impossible object exists in reality. In the discussion, however, what is present is the conception of the impossible and the judgment that it cannot obtain—not an external instance of the impossible.

For example, one can think about the impossibility of two contradictories both being true. Thinking about that impossibility does not instantiate the contradiction in the external world.

4. The mental status of impossibility

أن الامتناع اعتبار ذهني
Impossibility is an intellectual consideration.

The intellect may judge something impossible. That judgment is mentally present, but the object denied by the judgment does not thereby exist externally. The existence of a judgment differs from the external existence of its supposed object.

The faulty inference is: “We can speak of the impossible; therefore the impossible exists outside the mind.” The premise establishes intelligibility, not an external instance.

5. Confusing the representation with its object

ومنها: أخذ مثال الشيء مكانه
Another fallacy is substituting a representation of a thing for the thing itself.

The text uses the image of fire: mental fire does not possess all the effects of external fire. “Every fire burns” cannot be transferred unchanged to a representation of fire and taken to mean that imagining fire must cause burning.

A representation makes its object intelligible; it does not inherit every material property or causal power of that object.

6. Comparing objects, images, and judgments

LevelExampleCorrect claim
External objectActual fireProduces heat under appropriate conditions
Mental representationA concept of fireMakes the meaning present to the mind
Logical propertyUniversality of the conceptConcerns applicability to many instances

The term “fire” appears in every row, but its respect of predication differs. Moving a judgment from one level to another without justification is a material error.

7. Two senses of existence in the commentary

The commentary discusses two respects of existence: a form in the mind representing an external thing, and an object considered only at the level of an intellectual notion. It also mentions different accounts among classical theologians and philosophers.

For the present logical purpose, being thinkable, existing outside the mind, and having external causal effects are different predicates.

The metaphysical debate should be kept distinct from the methodological lesson: a statement about a mental object does not, by itself, establish external existence.

8. Treating part of a cause as the complete cause

ومنها: أخذ جزء العلة مكان العلة
Another error is substituting one component of a cause for the entire sufficient cause.

The book imagines 70 people carrying a heavy stone over 70 farsakhs. Their collective accomplishment does not imply that each can carry the same stone alone for one farsakh. Their cooperation may be essential to the achievement.

Where an effect depends on several jointly operating conditions, an individual condition need not be sufficient to produce a proportional part of the same effect.

9. Misapplying an argument from greater priority

ومنها: إجراء طريق الأولوية عند الاختلاف
Another error is employing an argument from priority where the cases differ in the relevant respect.

An a fortiori inference works only when the property that grounds the ruling is shared and is stronger in the proposed case. If the two cases differ precisely in the relevant respect, the inference fails.

The book uses humans, birds, and the “rational soul” to show that sharing animality does not entail sharing every distinctive intellectual property.

10. Conditions for a sound a fortiori argument

Consider: “If a person cannot lift this light load, they cannot lift the heavier load.” It is reasonable only if the relevant circumstances are the same and no factor other than weight changes the task.

By contrast, “A bird lacks a given intellectual quality; therefore a human lacks it even more” fails if the human has a distinctive property not shared by the bird.

A sound argument from priority depends on a common and suitably strengthened ground, not a superficial resemblance.

11. Changing the respect of predication

ومنها: ما وقع من قلة المبالاة بالحيثيات وترك الاعتناء بها
Another fallacy results from neglecting the different respects under which a thing is considered.

A thing may be taken as a body, as a species, as an individual, or as a bearer of a property. A predicate true in one respect is not automatically true in another.

The same words can therefore remain in an argument while the relevant qualification shifts. Its verbal appearance is coherent even though its logical middle has changed.

12. The textbook’s example involving “white”

كل أبيض دخل في حقيقته البياض، وزيد أبيض
Whiteness enters the notion of whatever is white, and Zayd is white.

It does not follow that whiteness belongs to Zayd’s human essence. The first premise treats “white” under the descriptive notion of being white; the second calls an individual white because he bears that accident.

Whiteness may be included in the meaning of the adjective “white” without being included in the essence of the person to whom that adjective is applied.

13. Essence is not every feature of its bearer

“Zayd is white” may be true, but “Zayd is human” and “Zayd is white” are not predicates of the same essential status. Humanity concerns his species, while whiteness may be a removable accidental property.

If Zayd’s complexion changes, he does not cease to be human. Thus an accidental attribute may be truly predicated of someone without becoming part of the definition of their essence.

This reconnects the fallacy to the earlier distinctions among the five predicables.

14. The mistaken transitivity of resemblance

ومنها قولهم: مماثل المماثل مماثل
Another claim is that whatever resembles something resembling a third thing must resemble the third.

The text uses a human, a date palm, and a stone. A human might resemble the palm in one respect and the palm the stone in another. It does not follow that the human and stone resemble each other in the same respect.

The unqualified word “similar” conceals the shift in the particular feature on which each comparison rests.

15. Resemblance needs a stated common respect

Example:
A human and a tree both grow.
A tree and a pillar can both be upright.
It does not follow that a human and a pillar share the property of biological growth.

A relation can be transitive only where the same relation under the same relevant restriction is preserved. Numerical equality is transitive: if A = B and B = C, then A = C. Resemblance in shifting respects is not the same kind of relation.

16. Privation is not mere absence

أخذ العدم المقابل للملكة مكان الضد والنقيض
Substituting privation for a contrary or a simple contradictory negation.

Privation is the lack of a capacity naturally appropriate to that kind of subject—for example, blindness in a being normally capable of sight. Mere absence of sight applies more broadly, even to things for which sight is not expected.

Consequently, “does not see” and “is blind” are not interchangeable predicates for every subject.

17. Why a wall is not blind

The text notes that not moving does not always amount to rest in the specialized sense applicable to what can move; similarly, lacking sight does not make a wall blind.

Example: Classifying inanimate matter as at rest and calling a wall blind in a technical sense.

The argument moves from mere absence of motion or vision to a predicate requiring a specific natural capacity of the subject. Ignoring this restriction makes the inference invalid.

18. Comparing absence, privation, and contradiction

TermConditionExample
Simple negationThe property is absentA wall has no sight
PrivationAn appropriate capacity is missingLoss of vision in an eye naturally able to see
ContrarietyOpposing positive qualitiesWhite and black

The kind of subject and its relevant capacity must be preserved when these different oppositions are used in an inference.

19. The celebrated puzzle: how can the unknown be sought?

لا يمكن تحصيل المجهول
“The unknown cannot be acquired.”

The puzzle argues: if what we seek is already known, searching is pointless; if it is wholly unknown, how can we recognize the answer when we find it? It then concludes that acquiring new knowledge is impossible.

The argument treats known and unknown as absolute descriptions in every respect. But the same object can be known in one respect and unknown in another.

20. Knowing a thing under one description but not another

The text’s example is a missing servant. The searcher knows the person's identity but not where he currently is. Discovering his location adds knowledge about his whereabouts, not knowledge of his previously recognized identity.

Similarly, someone can know Zayd by name but not know that he authored a certain book. Establishing the authorship provides new information.

The resolution is known in one respect, unknown in another. Knowledge does not have to be all-or-nothing.

21. A proposed proof that presupposes its conclusion

المدعى ثابت
“The claim is established.”

The text describes a traditional dialectical fallacy attempting to guarantee that any proposed claim can be declared established. It starts from supposed truth conditions concerning the claim or its contradictory without first justifying those assumptions.

The important test is whether the reasoning uses an independently warranted premise or quietly assumes that the desired conclusion is already secured. The latter can amount to a sophisticated form of begging the question.

22. Truth, failure of truth, and the contradictory

Take the proposition “Zayd is standing.” In classical bivalent logic, if that fully specified proposition is false, its true contradictory holds. The rule cannot be transported unchanged across different times, counterfactual suppositions, or subjects.

“Zayd is standing” and “Zayd is not standing” are contradictories only with the same relevant subject, time, and other conditions.

The text’s closing paradoxes repeatedly shift between what is true in a given supposition and what follows in another. One must fix the supposition and the proposition before applying the rule of contradiction.

23. Actual and counterfactual suppositions

The book distinguishes an actual supposition from a hypothetical or counterfactual supposition. That a proposition is true in reality is not the same as saying it holds under every imagined scenario.

If the major premise quantifies over hypothetical cases while the minor concerns only the actual situation, the middle term is no longer identical in respect.

The apparent syllogism cannot therefore deliver the conclusion claimed without an additional premise bridging the two contexts.

24. A quantifier shift between major and minor

A statement such as “Whenever Zayd's standing fails to hold, his non-standing holds” can be valid under a fixed evaluation. Treating it as a universal law across every kind of supposition and combining it with a premise about one particular scenario requires further justification.

The defect: the major speaks of “every case” under one interpretation, while the minor concerns the actual status of a case under another.

The repair is to state explicitly which domain of suppositions each premise quantifies over.

25. A frequently occurring general fallacy

المغالطة العامة الورود
A widely occurring fallacy.

The text analyzes an argument that tries to establish a claim by hypothesizing what follows from the failure of that claim and from the hypothetical truth of its contradictory. The risk is conflating proof of the original claim with what was merely supposed for the sake of argument.

The task is not simply to notice the conditionals “if” and “whenever,” but to fix what their antecedents and consequents assert, and under which modal or hypothetical status.

26. Conversion by contraposition preserves the right scope

The closing objection derives a new statement by contraposing a conditional. The commentary warns that the antecedent and consequent must not change their scope of generality or particularity while being transformed.

For example, “Every A is B” can support “Every non-B is non-A” under the appropriate interpretation. But this procedure cannot be transplanted indiscriminately to complex conditionals, modalities, or suppositions.

A valid transformation must preserve the relevant domain, negations, and meanings of the two sides.

27. The text’s warning against an unwarranted inverse

The text expresses surprise at an argument that appears to contrapose a sound conditional yet yields a conclusion incompatible with the original claim. The difficulty arises because the two propositions preserve a similar verbal form while not preserving the same logical domain.

If the original concerns the failure of a claim under a certain supposition, its contrapositive must concern the contradictory under that same supposition. Changing the domain produces an invalid inference dressed as a familiar rule.

The lasting lesson is to preserve the scope and respect of evaluation throughout the proof.

28. A consolidated map of the remaining fallacies

ErrorInvalid move
Mental predicateFrom a concept to external existence
Image and objectGiving mental fire the effects of physical fire
Part of a causeAssigning a collective result to one member
ResemblanceAssuming transitivity across different respects
PrivationTreating all absence as a missing capacity
Scope and contrapositionMixing judgments across suppositions

The common issue is a shift in the subject, respect, or domain between premises and conclusion.

29. A five-part test for suspicious arguments

A practical sequence for analyzing a difficult syllogism:
1. Does each term retain its meaning?
2. Has a predicate of a mental concept been applied to an external object?
3. Is the alleged cause complete or only a contributing part?
4. Are the relevant respect, time, and supposition held constant?
5. Does the conclusion follow, or is an unstated assumption needed?

If the argument fails, identify the defective premise or transition rather than merely replacing the conclusion.

30. Conclusion of the fallacies chapter

Correct terminology and familiar syllogistic language do not suffice for a sound argument. The respect of predication, identity of meaning, sufficiency of causes, and scope of suppositions must all remain fixed.

Confusing mental concepts with external objects, images with things, partial causes with complete causes, unqualified resemblance with a transitive relation, or contradictories across shifting suppositions can produce apparently compelling but invalid arguments.

This concludes the source’s chapter on fallacies. The next part is its closing chapter (khātima), beginning with the subject matter of a science.