Thomas Aquinas on Divine Simplicity

In their metaphysical inquiry into God, what He is and how He is to be understood, medieval theologians, trained in the conceptual language of Greek philosophy, placed the attribute of simplicity at the forefront. For many of them, simplicity was the central defining characteristic of God’s nature. The Scholastics saw simplicity as the first of a series of divine attributes, including eternity, unchangeability, and immateriality, which are characteristic of how God is portrayed in classical theism. The natural theology behind classical theism is not a thing of the past; it still has its contemporary defenders, especially among philosophers inspired by the great medieval theologian Thomas Aquinas. I mention well-known scholars such as Eleonore Stump and Norman Kretzmann, both of whom have argued in their writings for the viability of the doctrine of divine simplicity (I especially recommend their essay, “Absolute Simplicity” in Faith and Philosophy 2 [1985], 353-82, as well as Stump’s book, Aquinas). Others like Rudi A. te Velde could be mentioned as well (note his book, Aquinas on God).

There are, however, contemporary Christian philosophers, especially from the recent Reformed tradition, who have critical reservations about this scholastic doctrine of simplicity. I mention here Alvin Plantinga (Does God Have a Nature?) and especially Nicholas Wolterstorff (note his essay, ‘Divine Simplicity’, in Philosophical Perspectives [1991], 5:531-552). Wolterstorff argues that the notion of simplicity, which denies all distinctions in God, is at odds with how God is spoken of in the context of Christian worship (see his book, The God We Worship). The main problem for Wolterstorff is that the thesis of divine simplicity reduces God’s being to a property or a mere abstract object. As such, according to Wolterstorff, simplicity conflicts with God’s personal character. Before discussing these objections, let us first explain what Thomas means by simplicity as applied to God and how it functions within his metaphysical approach to the reality of God.

Simplicity as Understood by Thomas Aquinas

It is not easy to explain in a few words the meaning of simplicity and what it says about God. One can compare the scholastic simplicitas as applied to God with our common use of the word ‘transcendence.’ God is often said to be transcendent, a word used to locate God beyond the world as the domain of human experience. ‘Transcendence’ is a typical term of reflection; it is not meant to characterize God directly as an object of religious belief, for example when we say that God is just or compassionate. ‘Transcendence’ is not a word of faith, but it says something about the extraordinary reality that people reference when talking about God, that is, a ‘transcendent being’ who is not part of the world, not existing as a creature among other creatures, but rather as the source (‘Creator’) of the being of all that exists. Similarly, the attribute of simplicitas is used to express the fact that God is not a being among other beings but is radically different from everything by virtue of His greatness and perfection.

In the Bible, God’s transcendence is often indicated by emphasizing his unknowability: God is above all that which can be expressed by human speech and thought. God is not like us. This motive plays a central role in the tradition of apophatic (negative) theology, especially associated with the name of Pseudo-Dionysius the Areopagite (an anonymous Neoplatonic theologian who wrote somewhere in the 6th century), but also prominent in Thomas’s approach to the question of God. We cannot know, Thomas says repeatedly, what God is, but only what God is not (quid non sit). For him, simplicity is part of this negative approach to God; it is a way of saying that God, unlike all that is created by God (‘his effects’), is not in any sense composed, that is, made up of parts (for example, the composition of form and matter). In the Bible, God’s transcendence is often indicated by emphasizing his unknowability: God is above all that which can be expressed by human speech and thought. Click To Tweet

There is no composition in God; his being is not internally differentiated. God is characterized by absolute identity. This absolute identity can be explained in terms of predication. Everything that is said about God is said in strict identity with God himself. No predicate denotes anything that is a part of God, distinct from God himself. For example, if we say that God is good, this simply means that God is his goodness. There is no difference in God between ‘being God’ and ‘being good.’ Of course, we cannot speak meaningfully of God except by treating him logically as a subject with properties; human thought and language are adapted to the categorical structure of objects of human experience. In a sense, we can only speak of God according to the model of an object of experience, a concrete something (or someone) of a certain kind that is so and so (e.g. wise and loving) and acts so and so (e.g. God knows, creates, foresees, saves, etc.). So, the way in which we signify God in our language is not at all ‘simple’, it represents God in a way comparable to an object of experience. This is why, in a religious tradition, we often tend to think of God as a kind of enlarged human person endowed with superqualities. At the same time, however, most religious people, when they speak of God, are generally aware of the mystery of God, of his radical transcendence. Biblical texts, religious songs, liturgical phrases, all bear witness to God’s radical transcendence, which goes hand in hand with His most intimate presence in His creation.

For Thomas, the seemingly simple question ‘what is God’ is central to his theological inquiry. At the beginning of his Summa theologiae we see him questioning the ontological reality of God by means of a categorical analysis. This endeavour is a philosophical analysis that seeks to determine the intelligible character of a thing (questio quid sit) and express it in the form of a definition. The point, however, is that we cannot define God; what God is can only be characterised, in relation to the categorical structure of our experience, negatively and indirectly on the basis of creatures, that is, the world as we know it. On the basis of creatures, we come to know, first, that God exists (by means of the proofs of God’s existence) and, secondly, what He must be “as the first cause of all things, exceeding all things caused by Him.” For example, if we say that God is good, this simply means that God is his goodness. There is no difference in God between ‘being God’ and ‘being good.’ Click To Tweet

From Effect to Cause

It is in the light of this indirect approach to God from ‘effects’ that the meaning of simplicity becomes clearer. The effects are the objects of human experience; they are objects composed of form and matter, subject and accident (property), concrete individual and its nature, essence and existence. This last type of composition is the most important; for Thomas, each creature is a particular essence, which has existence but is not identical with its existence (esse). All things are, but each in its own way; it is this but not that, that is, a particular thing that does not have the fullness of being. But God, who is the creative source of all things, is not a particular thing that has being; He must be identical with His being, so that He has the fullness of being, the plenitudo essendi.

Proceeding from effect to cause, Thomas follows the negative way of simplicity. We must deny the cause the compositional structure characteristic of the effects. Yet, there is a complication. Simplicity is usually associated with parts. The composed whole is analysed into its simple parts. While the whole is referred to in concrete terms, the parts are referred to in abstract terms. For example, a being (ens) is concrete, but its infinitive form, esse, is abstract. If God is said to be simply esse without any addition, then he is, it seems, regarded as an abstract object. Such an abstract object cannot be the personal God of religious worship, according to Wolterstorff, the God who is described in a concrete and personal language according to His interaction with human beings.

Thomas is aware of this problem, which he addresses in the following text: “We cannot speak of simple things [like God] except in the manner of composite things from which we derive our knowledge [like objects of human experience]. Therefore, when we speak of God, we use concrete nouns to signify His existence, because ‘in our world’ only those things exist which are composite, and we use abstract nouns to signify His simplicity.” (Summa Th. I, q.3, a.3, ad 1) We may, Thomas says, use abstract words to signify the simplicity of God (God is life itself, God is goodness itself), but since simplicity ‘in our world’ is associated with being imperfect and partial, we must correct this false implication by using concrete words to express the fact that God is a subsisting and perfect reality (and thus not an abstract object). Thus, we must say that God is most simple and perfect, both abstract and concrete at the same time. For Thomas, God is the unity of simplicity and perfection. For Thomas, ’person’ is first and foremost a word that characterises God in His internal Trinitarian differentiation, the persons of the Father, the Son and the Spirit. Click To Tweet

I am not sure that this will satisfy Wolterstorff. The conflict may be deeper and more fundamental. Thomas argues that God is a subsisting reality with an intellectual nature. What subsists in an intellectual nature can be called a ‘person.’ So God is a personal reality (though very different from human persons!). For Thomas, assigning the term person to God is not the same as describing God according to the way we experience Him and are related to Him as an object of religious worship, e.g. a God who knows us, loves us, who is assumed to answer our prayers, who takes care of His creatures, and so on. For Thomas, ’person’ is first and foremost a word that characterises God in His internal Trinitarian differentiation, the persons of the Father, the Son and the Spirit. This differentiation does not contradict the simplicity of God’s nature; there is one God, one nature in three persons.

It is important to recognise the difference between the concrete biblical vocabulary in which God is described in His interaction with human beings, that is, as we experience Him in the context of religious faith, and the abstract philosophical language used in metaphysical-theological inquiry into the reality of God. Thomas’s speculative theological programme is to develop a conceptual framework which seeks to define, in an indirect and negative way, what it is to be God. Such a conceptual framework does not describe God from a direct religious perspective, but it does explain the presuppositions underlying the concrete God-talk of a religious tradition.

Image credit: Torsten Reimer