In the previous article, “Divine Simplicity ‘God without Parts,’” we discussed the doctrine of divine simplicity, that is, God’s absolute oneness and indivisibility. The previous notes in that article aid us in beginning to understand who God is and how the doctrine of divine simplicity helps us talk about him. In this article, we will consider five implications of divine simplicity as follows: (1) God has no deeper or multiple ontological layers or realities, or to put it positively, all that God is, he fully is; (2) there is only one divine essence and thus only one God; (3) God’s will is one; (4) God’s external works are undivided; and finally, (5) God’s communicable attributes in his relations towards creatures are never at odds.
Five Implications of Divine Simplicity
1. No Ontological Layers: Attributes, Existence, and Persons
Since God is simple, there are no ontological layers in God. This means everything that God is, he wholly is. Therefore, God’s attributes are not something other than God himself. God’s existence is not something severed from his perfections, and his perfections are not some sort of addition to who he is. Holmes helpfully puts it this way: “It is not that God, being God, could then decide whether to be just, good, or eternal. Rather, all that God is, he is necessarily and eternally. God’s life is not a composite of his essence and those things he has chosen to embrace in addition; God’s life is simple.” Consequently, we cannot say God’s existence is some deeper reality other than his attributes or vice versa. Due to the doctrine of divine simplicity, we cannot say there are deeper realities in God, that is, more important or foundational, ontological layers in God. Again, put positively, all that God is, he wholly is.
This must also mean then that God’s existence is not different than his essence. Put positively, God’s existence and his essence are identical. They are not two severed realities; they are one. After affirming divine simplicity, Aquinas states in the Summa, “God is not only His own essence … but also His own existence.” Hence, his essence and existence do not differ. For all the things that are apart from the essence must be “caused … by some exterior agent,—as heat is caused in water by fire. Therefore, if the existence of a thing differs from its essence, this existence must be caused by some exterior agent….” However, God is not dependent for his existence, for God is the first efficient cause and is thus a se. Accordingly, it is impossible for God’s essence and existence to differ. “Therefore His essence is His existence.”
Though the trinitarian nature of this truth will be further expounded upon in a future article, a brief note is fitting. A person of the Godhead is not something other than the essence or vice versa. That is, a divine person is not severed from the divine essence. As Webster says, “the persons of the Godhead are not distinguished from the divine essence realiter,” and further, “This is not to reduce the persons back to some anterior unity … but simply to state that the persons are inseparable from the essence, and the essence inseparable from its threefold modification.” How then do we understand the reality of a divine person? Webster aids our efforts: “Divine persons … are not fractions of the divine essence, or some reality additional to that essence; they are irreducible modes of that essence.”
To sum up this point, because God is one who is simple, one cannot ascribe priorities in God. Namely, there are no ontological levels in God. This means that divine attributes or divine persons are not something additional to God. It is not as if God existed and then took on more—something else. Rather, since God is simple, all of what he is, he wholly, necessarily, and eternally is. As he himself puts it, “I AM WHO I AM” (Exod 3:14).
2. One Divine Essence
Since God is simple, it necessarily means that his essence is one and that there is no other. Put differently, there is only one divine essence—meaning there is only one God. As Aquinas says, “God Himself is His own nature.” God’s oneness is incommunicable to any other being since he is simple. Metaphysically, this should not be confused to mean that God is one in number. God is not a material genus. Instead, he is one in a way that is “convertible with being”—that is, he is one in essentiality. Every being is one either compositely or simply. Yet only God is simply one (or, one in simplicity), since he is absolute and supreme being. And for him to be supreme being is for him to be undivided being, or “supremely undivided inasmuch as He is divided actually, nor potentially, by any mode of division.” Not only can he not be divided, he cannot be multiplied (which would assume material existence) or supplemented with his own essence. God is perfectly, supremely, and absolutely one according to his simplicity.
From the very beginning of God’s drama, it is written that one God alone creates and has dominion. “In the beginning God [אֱלֹהִ֑ים] created the heavens and the earth.” This same God is later revealed as the very YHWH (Yahweh) who “alone stretched out the heavens, who spread out the earth by myself” (Isa 44:25; cf. Job 9:8). God states emphatically through Isaiah that “I am YHWH [יְהוָה], and there is no other; apart from me there is no God [אֱלֹהִ֑ים]” (Isa 45:5). The Shema tells Israel to hear that “YHWH our God, YHWH is one” (Deut 6:4). Even in the New Testament (NT), “there is one God” (1 Tim 2:5; cf. 1 Cor 8:6; Eph 4:4), and “God is one” (Gal 3:20). While these NT texts mainly pertain to the person of the Father, the Son and the Spirit are also revealed to be one with the Father en substantia (in substance). Thus, God in his simplicity is one in his essence.
3. One Divine Will
If God is simple, there is only one will in God. Since God is not composed of parts, he is therefore not composed of multiple wills. And, as has been shown before, he is one in essence; thus, he is one in will. “As his intellect is his own existence, so is his will.” That the triune God is one in will is revealed most clearly in John’s Gospel. Before the Lord ascended into heaven, he promised his disciples that “When the Spirit of truth comes, he will guide you into all truth, for he will not speak on his own authority, but whatever he hears he will speak…” (John 16:13). What the Spirit “declares” will be “what is mine” (16:14)—that is, the Son’s words (cf. 14:26). The Spirit of the Son speaks the words of the Son. And the words of the Son, he who came “down from heaven, not to do my own will but the will of him who sent me” (6:38), are not his, “but the Father’s who sent me” (14:24; cf. 7:16; 12:49; 14:10). The Son, as the Word of the Father (1:1), speaks the words of the Father, and the words of God disclose the will of God. Like the heat and radiance of the sun, so the will of the Son and the Spirit cannot be separated from the will of the Father.
4. Undivided in External Works
Since God is simple, God’s external works are undivided with reference to the divine persons. This naturally follows the fact that God is simple, because if he is simple, he is one, and if he is one, then there must be unity in his external work(s). In trinitarian terms, this means that the persons of the Godhead do not work in opposition to each other. For example, the Father does not do one thing in contradiction or opposition to the other persons. Further, this means that a person does not work severally from the others. Instead, all persons are active in their own personal manner, acting upon on the one will of God. Hence, the rule: opera Trinitatis ad extra indivisa sunt (the outer works of the Trinity are undivided). 
Simply stated, because God is simple and there is no division in God, his outer works are also undivided. Put positively: There is unity in God’s external work(s). This is clearly manifested in the baptism: The Son comes out of the water, the Spirit descends, and the Father is pleased. This means that God’s outer works reveal his inner being: As God has one undivided (simple) essence, so his works are undivided. As Emery puts it: “The three divine persons act inseparably, in virtue of their common divine nature….” This, however, is not to say that there is no distinction within the undivided work of God. Surely there are distinctions within God’s indivisible, external works, for the Father did not die on the cross (contra patripassianism). There are distinctions even in undivided work and the two are not at odds. Webster puts it this way: “Common activity is not indistinguishable activity.”
To sum up this point, because God is simple, there is a unity in God’s external works. As God works in creation, provision, salvation, and consummation, his action really is undivided with reference to the persons of the Godhead, as he himself is undivided.
5. God’s Communicable Attributes and His Dealing with Creatures
Since God is simple, God’s communicable attributes in his relation toward creatures are never at odds. Just as in his incommunicable perfections, God cannot decide to be a se and then decide to be immutable. All of that which God is, he is. This is even so in his relation(s) to creatures. For example, God really does mercifully bring people to saving faith in Christ, and he really does justly damn unbelievers to eternal, conscious torment in hell—and these two works whereby his mercy and justice are displayed are not at odds. One may ask: How is mercy compatible with justice in God? How can God be simultaneously merciful and just? Divine simplicity helps us give an answer. When these works are studied under the lens of who God is as one who is simple, then one can see that God’s communicable attributes of mercy and justice are not pitted against each other because God’s life is one. Holmes wonderfully summarizes:
The doctrine of divine simplicity, properly understood, will insist that God’s perfections are not dispensable or separable. God cannot choose to lay aside his mercy, justice, or love without ceasing to be who he is; and God’s justice and mercy cannot be set against one another as if God were pulled in different ways, or faced some sort of quandary to which he needed to find a solution. Every act of God is simultaneously absolutely just and perfectly merciful, if God is indeed properly named as both just and merciful.
Since God is as one who is simple, actus purus (pure actualization [i.e., one who is pure and full reality]), and eternal, God can be both merciful and just.
We have just presented some of the implications of divine simplicity, that is, God’s indivisibility. God is one who is without parts; he is one, unified and indivisible being. Necessarily then, there are no ontological layers in God. There is only one true God, there is one will in God, God’s external works are undivided (opera Trinitatis ad extra indivisa sunt), and God’s attributes as revealed in his external works are never at odds with each other. This is not to restrict God, but rather it is meant, in earnest, to show God’s incomprehensible glory in his perfections.
The doctrine of divine simplicity has played a major role in theological inquiry. before turning to God’s triunity, next week we will cover why and how this study—the study of God’s being/essence, which many consider as “metaphysics”—aids worship.
 “Deeper” here pertains to ontological priority, not our intellectual understanding of God.
 Holmes, “A Simple Salvation? Soteriology and the Perfections of God,” 38.
 Aquinas ST, 1.3.4.
 Ibid., 1.3.4.
 Ibid., 1.3.4.
 Ibid., 1.3.4.; cf., 1.11.3.
 John Webster, God without Measure, 1:87.
 Webster, God without Measure, 1:88.
 Thomas Aquinas, ST, 1.11.3.
 Ibid., 1.11.3.
 Ibid., 1.11.3.
 Ibid., 1.11.1.
 Ibid., 1.11.4.
 Ibid., 1.11.4.
 One purpose of the Genesis creation narrative seems to be to actually distinguish the one Elohim of the Jews from the pantheon of Near-Eastern gods. The “two great lights” of Genesis 1:16, for example, were worshipped by Moses’ contemporaries as the “sun” and “moon” gods—yet God shows his dominion over them by separating them. For more on this topic, see John Walton, The Lost World of Genesis One (Downers Grove, IL: IVP Academic, 2009).
 As Richard Bauckham puts it, “However diverse Judaism may have been in many other respects, this was common: only the God of Israel is worthy of worship, because he is the sole Creator of all things and the sole Ruler of all things” (Richard Bauckham, Jesus and the God of Israel: God Crucified and Other Studies on the New Testament’s Christology of Divine Identity [Grand Rapids: Eerdmans, 2008], 183).
 See esp. John 1:1; 10:30; 20:28; Titus 2:13; 2 Pet 1:1; Rev 22:13 (cf. 1:8; Isa 41:4; 48:12).
 See esp. Acts 5:3-4; 2 Cor 3:17 [poss.]; 13:14; 2 Pet 1:21 (cf. 2 Tim 3:16); Heb 3:7-11 (cf. Ps 95:7-11).
 Aquinas, ST, 1.19.1.
 It may seem strange or out of method to speak of God’s external works on a treatise of the being of God. However, it is not only fitting to do so, but necessary, for there is no God that exists apart from the one who willed this history (implied in John Webster, “The Self-Organizing Power of the Gospel of Christ: Episcopacy and the Community Formation” in International Journal of Systematic Theology 3 no. 1 : 72). Now that can be taken in such a way that one may read it as God does not exist apart from this history and is thus dependent on this history. However, that would deny the doctrine of God’s independence—aseity—a doctrine we deeply affirm. Instead, when we say, “there is no God that exists apart from the one who willed this history,” we mean that the only God who exists ordains this history to be and he is immanent in this history and there is no other reality than this. Simply put, God wills this history to be, he is providentially present, and it is not otherwise. The only God that exists is the God who willed to create and re-create. There is no other reality.
 This notion will be further expounded in a later article.
 Emery, The Trinitarian Theology of St Thomas Aquinas, 349. Note that Emery says this in a particular section that also expounds the persons’ distinctions within the indivisible action.
 Webster, God without Measure, 94.
 Holmes, “A Simple Salvation? Soteriology and the Perfections of God,” 45.