How does Avicenna formulate the argument from contingency in "The Pointers and Reminders," and what is its relationship to the proof in Aquinas?

Avicenna — al-Shaykh al-Ra'īs (d. 428 AH/1037 CE) — formulated in "The Pointers and Reminders" (al-Ishārāt wa-l-tanbīhāt) the most precise classical formulation of the argument from possibility and necessity, which he called the "proof of the veracious" (burhān al-ṣiddīqīn). This formulation radically influenced Thomas Aquinas in the thirteenth century, although Aquinas modified the proof to align with his Christian theological framework. Understanding the relationship between the two formulations reveals a profound cross-cultural and inter-religious philosophical development.

Inadequate Responses to Avoid

From some defenders of Islamic heritage:

"Aquinas is merely a transmitter of Avicenna." A reductive oversimplification. Aquinas studied Avicenna deeply (through Latin translations), but he introduced substantial modifications reflecting his particular theological concerns. Fairness requires acknowledging both originality and influence.

"The proof of the veracious is stronger than the five ways." A comparison that needs precision. The two proofs differ in starting point and objective. Avicenna begins from analysis of the concept of existence itself; Aquinas begins from cosmic observation. Both have their strengths and weaknesses.

From some Western scholars:

"Aquinas corrected Avicenna's metaphysical errors." A claim needing context. The modifications Aquinas introduced were for theological reasons (such as rejecting the eternity of the world) more than purely philosophical corrections. Judging "correctness" requires clear criteria.

"Avicenna is a Neoplatonist, Aquinas a true Aristotelian." A simplification of philosophical complexity. Both blend Aristotelianism and Neoplatonism in different ways. Avicenna is Aristotelian in logic and natural philosophy, Neoplatonic in theology. Aquinas likewise integrates Neoplatonic elements despite his Aristotelian framework.

Why These Responses Are Inadequate

They share a failure to grasp the complex nature of philosophical influence across cultures. The relationship between Avicenna and Aquinas is neither simple transmission nor unilateral correction, but profound philosophical dialogue that shaped the development of Western metaphysics.

Avicenna's Formulation in "The Pointers"

In the fourth section (namaṭ) of "The Pointers and Reminders," Avicenna formulates the proof of the veracious with utmost precision. The proof begins from analysis of the concept of existence itself, not from observation of the world:

First Premise: Every existent is either necessary existence in itself (wājib al-wujūd bi-dhātihi) or possible existence (mumkin al-wujūd).
- Necessary existence: that whose existence is from itself, so its non-existence cannot be conceived.
- Possible existence: that for which existence and non-existence are equally possible with regard to itself.

Second Premise: The possible needs a determinant (murajjiḥ) that makes its existence prevail over its non-existence.
This determinant cannot be from the essence of the possible itself (otherwise it would not be possible), so it must be external.

Logical Analysis:
- If the determinant is possible, it too needs a determinant.
- Infinite regress in determinants is impossible (because a series of possibles all remain possible).
- Circular causation is impossible (that A determines B's existence and B determines A's existence).

Conclusion: We must arrive at a necessary existent in itself, which is the first determinant needing no determinant.

Avicenna emphasizes this is the "proof of the veracious" because it needs no consideration of created things, but begins from analysis of existence itself. The veracious "witness through Him, not to Him" — they argue from the Necessary Existent to others, not vice versa.

Avicenna's Development: Unity and Simplicity

Avicenna adds that the Necessary Existent must be:
- One: if there were two, they would share necessity but differ in something else, making them composite.
- Simple: having no composition, because the composite needs its parts.
- Knowing and powerful: because existential perfections flow from Its essential perfection.

Aquinas's Formulation in the Five Ways

Thomas Aquinas (d. 1274 CE) in the "Summa Theologiae" (I.2.3) formulates five ways to prove God's existence. The third way — from possibility and necessity — is closest to Avicenna's proof:

Formulation of the Third Way:
1. We find in nature things that are possible to exist and not exist (they are generated and corrupted).
2. What can possibly not exist was at some time non-existent.
3. If everything were possible, there would have been a time when nothing existed.
4. If nothing existed, nothing could begin to exist (from nothing, nothing comes).
5. Since things exist now, not everything is possible.
6. Something necessarily existent must exist.

Aquinas then adds: this necessary being either has its necessity from itself or from another. There cannot be infinite regress in derived necessities, so we must arrive at something necessary in itself, "and this everyone calls God."

Essential Differences Between the Formulations

Starting Point:
- Avicenna: Conceptual analysis of existence (from logical possible to necessary).
- Aquinas: Empirical observation (from perishing beings to necessary).

Structure:
- Avicenna: A priori proof needing no observation of the world.
- Aquinas: A posteriori proof beginning from observation.

Conclusion:
- Avicenna: The one simple Necessary Existent, with attributes deduced from necessity.
- Aquinas: The Christian God, emphasizing that attributes are known through revelation.

Treatment of World's Eternity:
- Avicenna: The world is eternal as an eternal effect of an eternal cause.
- Aquinas: Rejects world's eternity theologically, but accepts that the proof works even assuming eternity.

Influence and Development

Aquinas studied Avicenna through Latin translations from Toledo, especially via al-Ghazālī ("Aims of the Philosophers" translated) and Averroes. Clear influence in:
- Using the distinction between possible and necessary
- Rejecting infinite regress in causes
- Connecting simplicity and unity

But Aquinas modified the proof to align with:
- Christian theology (creation ex nihilo)
- Latin Aristotelian tradition
- Need for "bottom-up" proof suitable for natural reason

Contemporary Criticism of Both Formulations

Kant in "Critique of Pure Reason" attacked the ontological argument and its extensions. His criticism affects Avicenna's formulation more than Aquinas's, because Avicenna is closer to a priori proof. But contemporary defenders (like Mullā Ṣadrā and his followers) have developed responses.

Contemporary analytic criticism (Hume, Russell, Mackie) targets:
- The concept of metaphysical necessity
- The possibility of infinite regress
- The transition from logical necessity to actual existence

Contemporary Positions

Contemporary Muslim philosophers (Muhammad Bāqir al-Ṣadr, Morteza Motahhari) defend Avicenna's formulation with developments.

Neo-Thomistic philosophers (Gilson, Maritain) prefer Aquinas's formulation but acknowledge the depth of Avicennian insight.

Analytic philosophers of religion (Plantinga, Craig) develop new formulations benefiting from both traditions.

Where We Stand Today

The relationship between Avicenna's and Aquinas's formulations remains a subject of active research. Comparative studies reveal:
- The depth of Islamic influence on scholastic philosophy
- The possibility of philosophical dialogue across cultures
- The continuity of great metaphysical questions

Within the framework of rational evidencing (rajḥān ʿaqlī), both proofs contribute: Avicenna through deep conceptual analysis, Aquinas through connection to observation. Together they form part of the accumulation of rational evidence for the divine.

For Advanced Reading

─ Advanced level: Mullā Ṣadrā's critique of Avicenna and the fundamentality of existence (aṣālat al-wujūd)
─ Advanced level: Contemporary debate on metaphysical necessity
─ Avicenna, "al-Ishārāt wa-l-tanbīhāt" with commentary by Naṣīr al-Dīn al-Ṭūsī
─ Thomas Aquinas, Summa Theologiae I.2.3
─ Herbert Davidson, Proofs for Eternity, Creation and the Existence of God in Medieval Islamic and Jewish Philosophy (Oxford, 1987)
─ Jon McGinnis, Avicenna (Oxford, 2010)
─ "Classical Arguments: Contingency" page on the website