Reason, Sound Inference and Classifications of Knowledge

1. Reason as the Third Means of Knowledge

The discussion of reliable knowledge has already considered sound senses and truthful reports. Reason (ʿaql) is the third means: it can move from what is already understood to conclusions not directly perceived.

وَأَمَّا الْعَقْلُ وَهُوَ قُوَّةٌ لِلنَّفْسِ بِهَا تَسْتَعِدُّ لِلْعُلُومِ وَالْإِدْرَاكَاتِ
As for reason, it is a faculty of the soul by which it becomes disposed to knowledge and cognition.

Here a faculty does not mean muscular strength. Reason is the capacity for understanding and inference. The definition does not equate reason with all the propositions a person already knows; it emphasizes the capacity that makes knowledge possible.

2. Innate Disposition and the Capacity to Know

Reason is also explained as a gharīzah, an innate disposition. This refers to a basic capacity rooted in human nature, even though its use and development occur progressively.

غَرِيزَةٌ يَتْبَعُهَا الْعِلْمُ بِالضَّرُورِيَّاتِ
An innate disposition followed by knowledge of necessary truths.

The order is significant: a capacity is not identical with the knowledge that eventually follows from it. A child may possess the beginnings of rational capacity without consciously knowing every basic proposition. The distinction prevents confusion between potential, actual understanding and developed inference.

3. Sound Instruments: Reason Is Not the Same as Sensation

The phrase “when the instruments are sound” highlights the role of the means through which information becomes accessible.

عِنْدَ سَلَامَةِ الْآلَاتِ
When the instruments are intact or sound.

A person without sight may still reason, though information acquired through vision is unavailable. Likewise, an impairment of hearing does not by itself eliminate rational capacity. Sensory access and the faculty of inference are related but distinct.

A defect in one channel may restrict particular kinds of input. It does not justify the sweeping claim that reason or every kind of knowledge has disappeared.

4. Competing Accounts of What Reason Is

Scholars offered different accounts of the nature of reason: a faculty of the soul, a substance in some philosophical vocabularies, or a non-bodily reality connected with understanding and direction of action.

وَقِيلَ: جَوْهَرٌ
And it has also been said: a substance.

These terms should not be treated as interchangeable. Identifying the function of reason does not settle every metaphysical dispute about what kind of entity it is. The reliability of a sound inference is a further question, distinct from these competing descriptions of the faculty itself.

5. Four Stages of Intellect: Beginning and Habitual Capacity

A classical fourfold account begins with material intellect (al-ʿaql al-hayūlānī): the initial receptivity to intelligible knowledge, before its actual development.

The second stage is intellect by disposition (bi-l-malakah): familiarity with basic concepts and necessary judgments sufficient to make further inference possible. A learner who grasps equality, number and simple relations can begin reasoning through unfamiliar problems.

These are conceptual stages of intellectual readiness, not a fixed timetable attached to particular ages. They explain different relations between capacity and actual understanding.

6. Four Stages of Intellect: Actual and Acquired

The third level is actual intellect (bi-l-fiʿl): a developed capacity to derive conclusions from established principles, even when every conclusion is not presently being considered.

The fourth is acquired intellect (al-ʿaql al-mustafād), described in terms of the presence of intelligibles and a more complete realization of understanding.

Intellect by disposition means readiness through elementary knowledge; actual intellect means a formed power available for reasoning; acquired intellect concerns the present realization of intelligible knowledge. Possessing an ability is not identical with consciously entertaining every proposition it could produce.

7. The Philosophical Doctrine of the Active Intellect

Some philosophical systems described an active intellect whose emanation was said to account for human understanding. This is a historical philosophical model, not an undisputed statement of Sunni creed.

An account of ordinary reasoning may describe natural capacity, learning, evidence and valid inference without thereby demonstrating the existence or operation of that model. Such additional metaphysical claims require their own argument.

The lesson is methodological: accepting the efficacy of reason does not commit one to every philosophical theory in which the term “intellect” appears.

8. Where Is Reason Located?

Classical discussions locate or associate reason with the heart, brain or rational soul, depending on the school and the kind of evidence being considered.

References to the heart in scriptural and devotional language express important claims about understanding and inner responsibility, but do not automatically amount to a complete anatomical map. Observations about brain injury or cognition raise a different set of questions.

Disagreement about the seat of reason does not by itself defeat the claim that humans can know truths through valid reasoning.

9. Understanding What Is Present and What Is Absent

تُدْرَكُ بِهِ الْغَائِبَاتُ بِالْوَسَائِطِ، وَالْمَحْسُوسَاتُ بِالْمُشَاهَدَةِ
Absent things are understood through intermediaries, and perceptible things through observation.

Here “absent” need not refer exclusively to the theologically unseen. It may simply mean not directly present to the senses. Smoke, for instance, may prompt an inference about fire; a trace may disclose a past event.

Senses provide certain inputs, while reason can connect them to further conclusions. Neither all sensory experience nor all rational inference should be rejected merely because the two have different functions.

10. How Rational Inference Produces Knowledge

A rational conclusion requires sound premises and an appropriate inferential link between them. Invoking “reason” does not turn an unsupported guess into knowledge.

For example, “All humans are mortal; Zayd is human; therefore Zayd is mortal” has a valid structure, given its premises. “This object shines; therefore it must be gold” does not: many things shine.

Sound reflection (naẓar ṣaḥīḥ) means disciplined reasoning under appropriate conditions. The epistemic defense concerns this kind of inference, not every thought that happens to occur.

11. Different Forms of Objection to Rational Knowledge

Objections to rational knowledge take different forms. Some approaches restrict reliable knowledge to sensation; others distrust extensive theoretical reasoning; some philosophers particularly questioned certainty in metaphysics.

بِخِلَافِ السُّمَنِيَّةِ وَالْمُلْحِدَةِ فِي جَمِيعِ النَّظَرِيَّاتِ
In contrast to groups that disputed theoretical knowledge more generally.

These are historical classifications within the source's polemical setting. They should not be collapsed into one undifferentiated view. “How can we know without sense?” and “How can metaphysical arguments be certain?” require distinct analyses.

12. Mathematics and Metaphysics: Different Claims

Some critics conceded the usefulness of mathematics while expressing doubts about metaphysical demonstration because metaphysical thinkers disagreed so widely.

The objection contains two steps: (1) substantial disagreement exists; (2) therefore sound reasoning cannot produce knowledge in that field.

The second conclusion does not follow from the first without further argument. Divergence may also reflect false premises, omitted conditions or faulty inferences. A disputed conclusion is not thereby proof that valid inference as such is impossible.

13. Why Disagreement Does Not Invalidate Every Argument

أَنَّ ذَلِكَ لِفَسَادِ النَّظَرِ
That disagreement can result from defective reasoning.

فَلَا يُنَافِي كَوْنَ النَّظَرِ الصَّحِيحِ مِنَ الْعَقْلِ مُفِيدًا لِلْعِلْمِ
Therefore, disagreement does not contradict the proposition that sound reasoning produces knowledge.

Two people can reach different answers in arithmetic because one miscalculates; that does not invalidate arithmetic itself. Equally, disagreement in theology does not disprove every well-formed argument. It also does not prove a particular disputed conclusion: its premises and reasoning still require examination.

14. A Further Objection: How Is the Value of Reasoning Known?

A deeper objection asks how we know that valid reasoning can produce knowledge. If that principle is self-evident, why is it disputed? If it must itself be proved through inference, are we not attempting to establish inference by inference?

إِنْ كَانَ ضَرُورِيًّا لَمْ يَقَعْ فِيهِ خِلَافٌ
If it were necessary knowledge, disagreement would not occur.

وَإِنْ كَانَ نَظَرِيًّا يَلْزَمُ إِثْبَاتُ النَّظَرِ بِالنَّظَرِ
If inferential, proving reasoning by reasoning would be required.

The target is the epistemic authority of inference itself, not the truth of an individual example.

15. Can People Disagree About Self-Evident Truths?

The first half of the objection assumes that a necessary truth could never be denied. But immediate knowability and universal, flawless understanding are not the same claim.

Disagreement may stem from misunderstanding the terms, misconstruing the proposition, deliberate rejection or some failure of comprehension. The principle “the whole is greater than its part” illustrates why the relevant concepts must be correctly understood before classifying an alleged disagreement.

A disagreement alone therefore does not prove the nonexistence of necessary knowledge. One must ask whether the parties dispute the proposition itself or understand it differently.

16. What Makes an Argument Circular?

Circularity (dawr) occurs when the conclusion to be established ultimately presupposes itself. Suppose one witness is trusted solely because another vouches for him, while the second is trusted solely because the first vouches for him; without an independent basis the justification is circular.

Not every use of intellect in assessing a proof has this structure. The relevant question is whether the proposition under examination was already assumed in the premises.

Using a faculty and illicitly assuming the very conclusion that faculty is supposed to demonstrate are not identical acts.

17. Valid Inference Versus Every Particular Inference

A crucial distinction is between the claim that some valid inferences produce knowledge and the claim that every proposed inference is valid. Defending the first does not entail endorsing all the conclusions of every theologian or philosopher.

كُلُّ نَظَرٍ صَحِيحٍ مَقْرُونٍ بِشَرَائِطِهِ
Every sound instance of reasoning accompanied by its proper conditions.

Those conditions include clear concepts, justified premises and correct entailment. Calling reasoning “sound” is not a shortcut that exempts particular arguments from scrutiny.

18. General Rules and Particular Instances

The proposition “every sound inference yields knowledge” is general. Applying it to a particular argument requires a separate examination of that argument's premises and structure.

A rule about valid syllogisms is not identical with the assertion that this particular syllogism is valid. The latter requires inspection.

Confusing the general principle with an unexamined individual instance creates an appearance of circularity. Distinguishing them makes it possible to assess the argument more precisely.

19. Innate Understanding, Traces and Reports

The source invokes innate cognition, reasoning from traces or effects and reliance on reports to explain how knowledge is obtained. Reason is not confined to abstract syllogisms detached from evidence.

وَاسْتِدْلَالٍ مِنَ الْآثَارِ وَشَهَادَةٍ مِنَ الْأَخْبَارِ
Or inference from traces and attestation through reports.

Footprints may supply evidence of someone's passage; multiple reliable witnesses may establish an event through testimony. The two routes differ: the first depends on assessing relations between effects and causes, the second on evaluating the report and its transmission.

20. Self-Evident Knowledge and Its Limits

وَمَا ثَبَتَ مِنْهُ أَي مِنَ الْعِلْمِ الثَّابِتِ بِالْعَقْلِ بِالْبَدَاهَةِ
And what is established through reason immediately or self-evidently.

كَالْعِلْمِ بِأَنَّ كُلَّ شَيْءٍ أَعْظَمُ مِنْ جُزْئِهِ
As in knowing that a whole is greater than its part.

A self-evident judgment does not require a separately constructed chain of proof once its concepts are grasped. It does not follow that every person understands the terms at the same stage of education. Conceptual confusion may produce verbal disagreement without discrediting the underlying judgment.

21. Necessary and Inferential: More Than One Classification

Necessary knowledge can be contrasted with inferential knowledge, meaning knowledge obtained without a deliberate proof versus knowledge reached by reasoning through premises.

But classical authors also contrast “necessary” with acquired (iktisābī) knowledge, shifting attention from the presence of an argument to the role of a person's choice and effort in obtaining it.

These classifications need not coincide. Before discussing a disputed example, identify whether “necessary” means “without inference” or “not produced through chosen acquisition.”

22. Acquired Knowledge: Explanation and Inference

وَقَدْ يُخَصُّ الْأَوَّلُ بِاسْمِ التَّعْلِيلِ، وَالثَّانِي بِالِاسْتِدْلَالِ
The first may be called explanation through a cause, and the second inference from an effect.

One may move from a cause toward an anticipated effect, or infer a cause from its observed effect. A fire and smoke illustrate the two directions, but each concrete case requires a warranted causal connection.

Acquired knowledge is broader than formal syllogism; observation, experiment and chosen inquiry also play a role. Yet performing an intentional act does not by itself guarantee certain knowledge.

23. Reconciling the Two Uses of “Necessary”

A difficulty arises when someone deliberately looks or listens and then immediately perceives something. Is that knowledge “necessary” because it does not result from argument, or “acquired” because a chosen act produced access to it?

The answer depends on the classification. Under the non-inferential criterion it may count as necessary; under a criterion focusing on intentional acquisition it may be considered acquired.

The terms are not contradictory when used in distinct technical senses. In careful analysis, a classification must be judged by the definition its author is using.

24. Human Choice and the Creation of Knowledge

The discussion also distinguishes human choice and effort from the divine creation of knowledge. A person chooses to examine evidence or conduct an experiment, but this is not the same question as the ultimate creation of knowledge and its occurrence.

Two questions must be separated: by what route did a person obtain knowledge, and what is its ultimate ontological dependence? The former concerns epistemology and acquisition; the latter concerns divine agency.

Confusing them either obscures responsible human inquiry or treats ordinary means as independent creators of knowledge.

25. Integrated Conclusion and the Next Question

Reason is a faculty that prepares the soul for understanding. Capacity must be distinguished from realized knowledge, and sound inference from conjecture. Senses provide evidence about perceptible things; reason can connect established premises to conclusions beyond direct observation.

Self-evident knowledge requires no constructed argument once its concepts are clear. Inferential knowledge is obtained through reasoning. Necessary and acquired may also distinguish the role of personal choice and effort, depending on the technical usage.

Disagreement does not refute all valid reasoning, but every particular argument still needs examination. These distinctions frame the further question of whether inspiration (ilhām) qualifies as an independent source of knowledge.