In the teaching series What Is Reformed Theology?, Dr. R.C. Sproul makes the point that the theology of the Reformation was catholic, or universal. That is, the Protestant Reformers accepted the great ecumenical creeds, such as the Nicene Creed, that were formulated by the universal church early in church history. In these creeds, we find an emphasis on divine diversity—the Father, Son, and Holy Spirit are distinct persons. Yet these creeds also emphasize divine unity—the Father, Son, and Holy Spirit are one God. We may combine these ideas and say that the Father, Son, and Holy Spirit are one God, but the Father is not the Son or the Holy Spirit, the Son is not the Father or the Holy Spirit, and the Holy Spirit is not the Father or the Son. We cannot fully understand how God can be both one in essence and three in person, but we will fail to affirm biblical monotheism if we deny either point.
Having looked at divine diversity in our last study, we will comment more on divine unity today as we look to Matthew 28:18–20. Here we have a key text that points to the unity of the three persons in light of Their distinctions. Notice that baptism is to be done in the name (singular) of the three (plural). The three persons share one name, and this name is none other than Yahweh, the covenant Lord of Israel. The name Yahweh in itself often refers to the divine essence, or the divine attributes, for it is by this name that God revealed His deity to Moses. “I am who I am” in Exodus 3:14 comes from the same Hebrew root for the name Yahweh, and it is a revelation of God’s self-existence. Yahweh means that God has the power of being in Himself, that He depends on nothing other than Himself for His existence. We, on the other hand, depend on our parents and, ultimately, on God for our existence, and we need others to survive.
Divine unity, however, means that self-existence is not one particular component of God’s being. Our doctrine of divine simplicity tells us that we distinguish but do not separate God’s attributes. His self-existence is His holiness is His justice is His goodness. All three persons share the one name Yahweh and thus the unity of the divine essence, and all three persons share the divine attributes equally. From all eternity, the Father’s authority is the Son’s authority is the Holy Spirit’s authority. The Father’s holiness is the Son’s holiness is the Holy Spirit’s holiness. Everything that God is essentially, the three persons are equally. None is more God or less God than any of the others.