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.