Is God simple? When we think of God’s nature, “simple” probably isn’t the first thing that comes to mind. As the song says, “we stand amazed in the presence of Jesus,” and that is good. We should be amazed at the incomprehensibility of our God. We can understand him like a fly can understand us. His thoughts are not like ours and his ways are not like ours (Is. 55:8). So, why would we say God is simple?
The “simplicity of God” is seen in Scripture. In Deuteronomy 6:4 we read, “Hear, O Israel! The LORD our God, the LORD is one!” What does it mean that God is “one?” Moses did not deny the Trinity, instead, he declared the “oneness” or “simplicity” of God. In Exodus 3:14 God said, “I AM WHO I AM.” Then God said for Moses to tell them “ I AM has sent me to you.” This somewhat mysterious declaration of God’s covenant name is difficult for us. Part of the difficulty is seen in English when we read “I AM.” We are waiting for the direct object—I am ______. But that may very well be the point. God is God. He is not composite. He is not a collection of things. God just is God.
When we say that God is “simple,” we mean that God is not composed of parts. Origin wrote:
God, therefore, is not to be thought of as being either a body or as existing in a body, but as an uncompounded intellectual nature, admitting within Himself no addition of any kind; so that He cannot be believed to have within him a greater and a less, but is such that He is in all parts Μονάς, and, so to speak, Ἑνάς, and is the mind and source from which all intellectual nature or mind takes its beginning.
God is not assembled like a machine and does not have an assembler above him. God is not the sum total of parts or attributes. He is “simultaneously everything that all of the attributes reveal.” C. F. H. Henry wrote:
Evangelical theology insists on the simplicity of God. By this it means that God is not compounded of parts; he is not a collection of perfections, but rather a living center of activity pervasively characterized by all his distinctive perfections. The divine attributes are neither additions to the divine essence nor qualities pieced together to make a compound.”
The doctrine of divine simplicity teaches us that God is not composed of parts which are more fundamental than he is. God is the most fundamental, the first cause, the first reason, and the source of everything that is. There is nothing “in God” which is not “fully God.” All of God’s “attributes” are fully identical with “all of God.” All of God’s attributes are God and God is simultaneously all of God’s attributes. God’s essence is equal to his existence.
The doctrine of simplicity matters because it points us to the necessary unity of God. Since there are not a conglomerate of parts composing the divine nature, there is never any friction within God. God, and God alone, enjoys a singular perfect essence. Augustine said, “that which is called life in God, is itself His essence and nature.” This perfect simplicity is the nature of the Father, and of the Son, and of the Spirit. The Spirit is not composed of other parts from the Father. The Son is not built with parts different from the Father. Instead, the singular perfect essence exists in the Father, and in the Son, and in the Spirit as distinct persons though they share the same perfect essence.
Simplicity matters because it prevents us from pitting one of God’s attributes against another attribute. God’s goodness does not compete with his severity. God’s mercy does not compete with his justice. Henry described it this way:
“If God is noncomposite, and his essence and existence are identical, then all divine attributes are mutually inclusive. Each attribute in the nature of God interpenetrates every other attribute and no conflict or contrast among them is possible. God’s wisdom is his omnipotence, God’s omnipotence is his justice, God’s justice is his love, and so on. God and holiness, and God and love, are mutually exhaustive synonyms; Scripture itself testifies that “God is love” (1 John 4:16), and not simply that love is in God. No divine perfection is therefore inferior or subordinate to another; all God’s perfections are equally ultimate in the simplicity of his being.”
God’s attributes do not differ from his essence and his essence does not differ from his attributes. There is no standard which God must achieve. Rather, he is the standard by which all others are judged because he is perfect perfection. All that is in God is God. God is composed of God. There are no parts. He simply is God—perfect deity through and through. As Bavinck wrote, “on account of its absolute perfection, every attribute of God is identical with his essence.” Since God is simple, every good thing exists perfectly and infinitely in his essence. As Irenaeus wrote God is “the one entire fountain of all good things.”
 Origen, “De Principiis,” in Fathers of the Third Century: Tertullian, Part Fourth; Minucius Felix; Commodian; Origen, Parts First and Second, ed. Alexander Roberts, James Donaldson, and A. Cleveland Coxe, trans. Frederick Crombie, vol. 4, The Ante-Nicene Fathers (Buffalo, NY: Christian Literature Company, 1885), 243.
 Horton, The Christian Faith, (Grand Rapids: Zondervan, 2018): 228.
 Carl F. H. Henry, God, Revelation, and Authority, vol. 5 (Wheaton, IL: Crossway Books, 1999): 131.
 Augustine of Hippo, “On the Trinity,” in St. Augustin: On the Holy Trinity, Doctrinal Treatises, Moral Treatises, ed. Philip Schaff, trans. Arthur West Haddan, vol. 3, A Select Library of the Nicene and Post-Nicene Fathers of the Christian Church, First Series (Buffalo, NY: Christian Literature Company, 1887), 202.
 Carl F. H. Henry, God, Revelation, and Authority, vol. 5 (Wheaton, IL: Crossway Books, 1999), 132.
 Herman Bavinck, John Bolt, and John Vriend, Reformed Dogmatics: God and Creation, vol. 2 (Grand Rapids, MI: Baker Academic, 2004), 173.
 Irenaeus of Lyons, “Irenæus against Heresies,” in The Apostolic Fathers with Justin Martyr and Irenaeus, ed. Alexander Roberts, James Donaldson, and A. Cleveland Coxe, vol. 1, The Ante-Nicene Fathers (Buffalo, NY: Christian Literature Company, 1885), 333.