What is divine simplicity according to Aquinas, and how does it differ from the concept of "non-composition" in Islamic kalām?

Divine simplicity according to Thomas Aquinas (1225-1274) is one of the most precise and difficult concepts in classical philosophy of God. Comparing it with "non-composition" (ʿadam al-tarkīb) in Islamic kalām reveals deep similarities and subtle differences between the two philosophical traditions in their approach to God's transcendence beyond composition.

Inadequate Responses to Avoid

From some scholars:

"Divine simplicity is merely a translation of Islamic non-composition." This is imprecise. Despite similarities, there are important methodological and conceptual differences. Aquinas builds on Aristotle and Augustine, while Muslim theologians developed their concept in the context of debates about attributes and divine unity (tawḥīd).

"Non-composition in kalām is merely simple negation, while Aquinian simplicity is a complex theory." This is a misleading simplification. Muslim theologians, especially later Ashʿarites and Māturīdites, developed very precise theories about non-composition and its relationship to divine attributes.

From some believers:

"Divine simplicity negates attributes, which is heretical." This is a common misunderstanding. Aquinas does not negate attributes, but says they are identical with the divine essence. This is close to the position of some Ashʿarites ("attributes are identical with the essence").

The Structure of Divine Simplicity in Aquinas

In the "Summa Theologica" (I, q.3), Aquinas builds simplicity on several levels:

First Level: Negating material composition. God is not composed of matter and form (matter-form composition). This is clear because God is immaterial.

Second Level: Negating composition of essence and existence. In all created beings, essence (what the thing is) is separate from existence (that the thing exists). In God, essence and existence are identical. God is "subsistent being itself" (ipsum esse subsistens).

Third Level: Negating composition of essence and attributes. God's attributes (knowledge, power, mercy) are not accidents added to His essence. They are all identical with the divine essence. God's knowledge = God's power = God's essence.

Fourth Level: Negating composition of genus and difference. God is not a "species" under a "genus." He is not "being + rational + powerful," but transcends all genera.

Aquinian Conclusion: God is "simple" in absolute terms—there is no composition in Him of any kind. This leads to profound philosophical consequences: God is pure being, pure goodness, pure truth, and all of these are one thing.

Non-Composition in Islamic Kalām

Muslim theologians developed the concept of "non-composition" in multiple contexts:

Among Early Muʿtazilites: Negating composition was the basis for negating additional attributes. They said: God is knowing by His essence, powerful by His essence, not by additional knowledge and power. This was to avoid "multiple eternals."

Among Ashʿarites: They developed a middle position: attributes are neither identical to the essence nor other than it. They are "meanings subsisting in the essence." Non-composition for them negates spatial and temporal composition, but does not negate the subsistence of attributes in the essence.

Among Māturīdites: Closer to the Ashʿarites, with stronger emphasis on the unity of essence despite multiple attributes.

Among Muslim Philosophers (Ibn Sīnā, al-Fārābī): Closest to Aquinas. The Necessary Existent is absolutely simple, and His attributes are identical to His essence. Ibn Sīnā: "The Necessary Existent is one from every aspect."

Points of Similarity

1. Transcendental Motivation: Both traditions seek to transcend God beyond the imperfection associated with composition.

2. Negating Bodily Composition: Complete agreement that God is not a composite body.

3. Eternity and Necessity: Linking non-composition to God being eternal and necessary of existence.

4. The Problem of Attributes: Both faced the same challenge: how to affirm multiple attributes without composition?

Points of Difference

First Difference: Philosophical Starting Point. Aquinas begins from Aristotelian metaphysics (act/potency, matter/form). Muslim theologians start from kalām debates about divine unity and justice.

Second Difference: Conceptual Rigor. Aquinian simplicity is more rigorous: all attributes are completely identical. Ashʿarite non-composition allows for distinct "meanings" subsisting in the essence.

Third Difference: Theological Consequences. For Aquinas: we cannot know God's essence. For most theologians: we can know God's positive attributes.

Fourth Difference: Relationship to Revelation. Aquinas reconciles simplicity with the Christian Trinity. Muslim theologians focus on pure monotheism (tawḥīd).

Contemporary Critique of Divine Simplicity

Alvin Plantinga and Richard Swinburne rejected classical divine simplicity. Their argument: if God's mercy = God's justice, concepts lose their meaning. How can mercy be identical to justice?

Contemporary Defenses

Eleonore Stump and Brian Davies defend: simplicity does not mean that human concepts about attributes are identical, but that the divine reality they point to is one.

Contemporary Developments in Islamic Kalām

Contemporary thinkers like Saʿīd Fūda develop the Ashʿarite position in dialogue with contemporary philosophy. They emphasize that "neither identical nor other" is a balanced solution to the problem of composition.

Where We Stand Today

Divine simplicity remains a subject of lively debate. In the Catholic tradition, it remains official doctrine. In analytic philosophy of religion, it is a matter of discussion. In contemporary Islamic kalām, classical formulations are being reconsidered.

The Deeper Philosophical Point

Both concepts face the same tension: how do we maintain the richness of divine attributes while avoiding ontological complexity? Different solutions reflect different theological priorities.

For Advanced Reading

- Advanced level: Jeffrey Brower's contemporary critique of divine simplicity from the perspective of modern logic
- Thomas Aquinas, Summa Theologica I, q.3
- al-Rāzī, al-Muḥaṣṣal fī Afkār al-Mutaqaddimīn wa-l-Mutaʾakhkhirīn
- Eleonore Stump, "Simplicity" in A Companion to Philosophy of Religion
- Saʿīd Fūda, Tadʿīm al-Manṭiq
- Page "Concept: Divine Simplicity" on the website