Theology Proper
Divine Attributes: Aseity and Simplicity
God exists from himself alone and is not composed of parts.
The doctrine explained
Aseity names God's self-existence: he depends on nothing outside himself for his being, and everything else depends on him. Exodus 3:14, where God names himself 'I AM WHO I AM,' has functioned in the tradition as a scriptural anchor for this claim, though the philosophical development owes much to reflection on Acts 17:25, where Paul says God is 'not served by human hands, as though he needed anything.' Aseity is the ground for the Creator-creature distinction: God alone has being in himself, while all else has borrowed being.
Divine simplicity is the stronger and more contested claim that God is not composed of parts, whether physical, metaphysical, or logical. On classical simplicity, God's attributes are not separable components bolted together but are each identical to the single divine essence and to one another. God does not have goodness the way a creature has properties; God simply is goodness, wisdom, and power, considered under different aspects by the finite mind. This doctrine was developed to protect divine ultimacy: a composed being would depend on its parts and on whatever combined them, undermining aseity.
The classical sources are Augustine's City of God book 11, Anselm's Monologion and Proslogion, and Thomas Aquinas's Summa Theologiae Ia q.3, which argues from God's status as pure act, unmixed with potency, to the conclusion that in God essence and existence are identical. Aquinas draws on Aristotelian act-potency metaphysics filtered through the pseudo-Dionysian and Boethian traditions to argue that any composition would require a prior cause to unite the parts, which is impossible for the first cause of all things.
Reformed scholastics such as Francis Turretin and the authors of the Westminster Confession (2.1, describing God as 'without body, parts, or passions') affirmed simplicity as part of the broader catholic inheritance, seeing it as entailed by divine infinity and immutability rather than as a speculative add-on. Lutheran orthodoxy likewise affirmed simplicity while resisting any construal that would compromise the reality of the divine persons or the communicated attributes discussed in Christology.
Simplicity generates real theological payoff. It secures divine immutability, since a being with separable parts could in principle lose or gain them. It secures aseity, since composition implies dependence on components. It also shapes how theologians read language about God's 'parts,' such as 'the arm of the Lord,' as anthropomorphic accommodation rather than literal predication, and it disciplines talk about God's love, justice, and wrath as not being competing internal faculties but the one divine nature acting toward creatures under different relations.
Contemporary analytic theologians have raised sharp objections. If God is identical to each of his attributes, and each attribute is identical to the divine essence, it seems to follow that all divine attributes are identical to one another, so that God's mercy just is God's justice, which strikes many as counterintuitive or as flattening real distinctions we need for coherent worship and doctrine. Alvin Plantinga's Does God Have a Nature? pressed this worry forcefully, and it has generated an extensive contemporary literature defending, modifying, or rejecting strong simplicity.
A mediating position, sometimes associated with later Reformed and some Thomist authors, distinguishes a moderate simplicity, which denies that God is composed of really distinct metaphysical parts but allows a virtual or conceptual distinction between attributes grounded in the single divine essence considered under different formal aspects. This preserves most of the traditional payoff while blunting the sharpest logical objections, though critics on both sides regard it as either insufficiently robust or as smuggling composition back in through the conceptual side door.
Biblical basis
- Exodus 3:14God names himself as self-existent being, 'I AM WHO I AM.'
- Acts 17:25God is not served as though he needed anything, being himself the giver of life and breath.
- Psalm 90:2From everlasting to everlasting God is God, without beginning or dependency.
- Isaiah 44:6God declares himself first and last, with no God besides him.
- John 5:26The Father has life in himself, the root scriptural text for aseity applied within the Trinity.
- Malachi 3:6'I the Lord do not change,' cited for divine immutability tied to simplicity.
- James 1:17The Father of lights, with whom there is no variation or shadow due to change.
- Romans 11:36'From him and through him and to him are all things,' expressing God as ultimate source.
How the wording developed
- c. 400Augustine argues in City of God 11.10 that God is called simple because he is what he has, except that the persons are relative to one another.
- c. 1078Anselm's Monologion and Proslogion reason from God's perfection to his simplicity and self-sufficiency.
- 1265-1274Aquinas's Summa Theologiae Ia q.3 systematizes simplicity via act-potency metaphysics, arguing God's essence is his existence.
- 1300sDuns Scotus develops the formal distinction to allow real distinctions among divine attributes short of composition, softening strict Thomist simplicity.
- 1500s-1600sReformed and Lutheran scholastics incorporate simplicity into confessional theology, e.g. Westminster Confession 2.1 and Turretin's Institutes.
- 1600sSocinian and early Enlightenment critics reject simplicity as unbiblical philosophical speculation, prefiguring later analytic objections.
- 1980Alvin Plantinga's Does God Have a Nature? mounts an influential philosophical critique of strong divine simplicity.
- 2000s-presentAnalytic theologians such as Katherin Rogers, James Dolezal, and Jeffrey Brower debate modified versus classical simplicity in retrieval projects.
Misunderstanding vs. the actual claim
Not this: Simplicity means God is simple in the sense of easy to understand.
But this: Simplicity is a technical term meaning without composition of parts, not intellectual simplicity.
Not this: Aseity means God caused himself to exist.
But this: Aseity means God never came into being at all; self-causation is incoherent, self-existence is not.
Not this: If God is simple, the Trinity is contradictory.
But this: Classical theologians distinguish essence from the relations of origin among the persons, which are not parts but relations within the one simple essence.
Not this: Simplicity is a late medieval philosophical import foreign to Scripture.
But this: Its defenders trace it to biblical claims about God's unity, immutability, and self-existence rather than treating it as pure speculation.
Not this: Denying strong simplicity means denying God's unity or perfection.
But this: Many theologians who reject strict simplicity still affirm a real unity and perfection of the divine nature through other means.
Where Christians differ
- • Thomist Catholic theology holds strong classical simplicity, denying any real distinction between God's essence and existence or among his attributes.
- • Scotist and some later Catholic and Protestant scholastics allow a formal distinction among attributes while denying real composition.
- • Reformed and Lutheran confessional orthodoxy generally affirms simplicity as catholic doctrine, though contemporary Reformed analytic theologians are divided over how strictly to hold it.
- • Eastern Orthodox theology, following the essence-energies distinction of Gregory Palamas, affirms the divine essence is simple and utterly transcendent while God's energies, through which he is known and by which creatures participate in him, are really distinct from the essence, a construal Western Thomists often see as compromising simplicity.
- • A growing group of contemporary analytic theologians reject strong simplicity outright in favor of a more modest doctrine of divine attributes as necessarily co-instantiated but not identical.
The hardest question
If God's justice, mercy, and love are all strictly identical to one another and to the single divine essence, in what sense can we say anything true and distinct about God at all, rather than merely projecting our conceptual distinctions onto an undifferentiated reality, and how does this square with the real, non-illusory distinction of persons in the Trinity, since 'person' and 'relation' must themselves be reconciled with a metaphysics that otherwise excludes all parts and distinctions in God?
For further study
Primary and secondary sources on both sides of this question. Reading the strongest opposing case is part of the work, not a concession.
The Christian Faith — Michael Horton
A single-volume systematic theology that traces how each doctrine developed and where traditions divide.
The Christian Tradition (5 vols.) — Jaroslav Pelikan
The standard history of doctrinal development, indispensable for seeing when a doctrine was actually formulated.
God Crucified / Jesus and the God of Israel — Richard Bauckham
Shows that the highest Christology appears in the earliest sources, not centuries later.
Early Christian Doctrines — J. N. D. Kelly
Patristic doctrine described from the primary texts; the place to check what the Fathers actually said.