Pieper, Francis. Christian Dogmatics: Volume 1. St. Louis: Concordia Publishing House, 1968.
Chapter C3, “The Trinitarian Controversies”
Although modernist theology has said that the doctrine of the Trinity was developed in church councils, it is laid out clearly in the Scriptures as well as in Fathers before the Council of Nicea. Pieper sets out to detail arguments against first, those who would deny three persons in the Godhead, and, second, those who deny one essence of God.
Pieper identifies Unitarianism with its other titles, Monarchianism and Anti-Trinitarianism. He also observes that Monarchianism is divided into Modal or Dynamic forms. Modalists hold God as being one, revealing himself in different forms at different times. The persons of the Trinity, then, are simply different roles. Dynamic monarchianism holds Jesus to be a man like any other, but empowered by the indwelling spirit of the one God. To counter the Unitarian claims the Church has normally used three proofs: 1) The names of Father, Son, and Holy Spirit indicate separate persons. 2) each person is represented as carrying on actions. 3) The three are referred to in Scripture as separate persons.
On the other hand, Tritheists and Subordinationists both assign different natures, or types of being, to the persons of the Godhead. This denies the unity of the Godhead. Pieper builds a biblical case for the unity of the Godhead, with three persons, one nature, working together.
Chapter C4, “Objections to the Unity of the Godhead”
Pieper now discusses four objections to the unity of God. First, since Christ talks about the Father as the ‘only true God” it may be assumed that Jesus is some kind of subordinate. On the contrary, God the Father, Son, and Holy Spirit are of one essence. The Son is also the only true God.
A second objection says that since the Father is the source of the Son and that the Father and Son are the source of the Spirit there must be subordination. This is not necessarily so. Even in natural things it is not always the case, and Scripture clearly considers the three persons as unified.
The third objection Pieper states is that the Bible teaches subordination because the Father accomplishes tasks through the Son or the Spirit. yet agency does not necessarily require subordination.
A fourth objection is that Jesus says in John 14:28-29 that the Father is greater than the Son. yet Pieper considers this to be Jesus’ statement of his status before the Father during his time in a state of humiliation. It does not refer to his permanent nature.