Daily Reform, Romans 5:1-5
From the Reformer
When we profess to believe in one God, by the name God is understood the one simple essence, comprehending three persons or hypostases; and, accordingly, whenever the name of God is used indefinitely, the Son and Spirit, not less than the Father, is meant. But when the Son is joined with the Father, relation comes into view, and so we distinguish between the Persons. But as the Personal subsistence carry an order with them, the principle and origin being in the Father, whenever mention is made of the Father and Son, or of the Father and Spirit together, the name of God is specially given to the Father. In this way the unity of essence is retained, and respect is had to the order, which, however derogates in no respect from the divinity of the Son and Spirit. And surely since we have already seen how the apostles declare the Son of God to have been He whom Moses and the prophets declared to be Jehovah, we must always arrive at a unity of essence. We, therefore, hold it detestable blasphemy to call the Son a different God from the Father, because the simple name God admits not of relation, nor can God, considered in himself, be said to be this or that. Then, that the name Jehovah, taken indefinitely, may be applied to Christ, is clear from the words of Paul, “For this thing I besought the Lord thrice.” After giving the answer, “My grace is sufficient for thee,” he subjoins, “that the power of Christ may rest upon me,” (2Cor 12:8,9). For it is certain that the name of Lord (Kurios) is there put for Jehovah, and, therefore, to restrict it to the person of the Mediator were puerile and frivolous, the words being used absolutely, and not with the view of comparing the Father and the Son. And we know that, in accordance with the received usage of the Greeks, the apostles uniformly substitute the word Kurios for Jehovah. Not to go far for an example, Paul besought the Lord in the same sense in which Peter quotes the passage of Joel, “Whosoever shall call upon the name of the Lord shall be saved” (Acts 2:21, Joel 2:28). Where this name is specially applied to the Son, there is a different ground for it, as will be seen in its own place; at present it is sufficient to remember, that Paul, after praying to God absolutely, immediately subjoins the name of Christ. Thus, too, the Spirit is called God absolutely by Christ himself. For nothing prevents us from holding that he is the entire spiritual essence of God, in which are comprehended Father, Son, and Spirit. This is plain from Scripture. For as God is there called a Spirit, so the Holy Spirit also, in so far as he is a hypostasis of the whole essence, is said to be both of God and from God.
—John Calvin, Institutes
Pulling It Together
Therefore a man shall leave his father and his mother and hold fast to his wife, and they shall become one flesh. (Gen 2:24) However one tries to show that Three can be One, the explanation falls short of the glory we call God. This, however, is the finest biblical illustration (outside of the Trinity himself) of how plurality may be one. The best explanation of what we believe, however, comes to us in the Athanasian Creed: “This is the true Christian faith, that we worship one God in three persons and three persons in one God without confusing the persons or dividing the divine substance.”
© Mark E. Ryman, Daily Reform: Devotions with the Reformers