The essential Monotheism of Christianity is not saved in the West by saying there is “one God the Father”, as in all the Eastern creeds, but the theologians teach the unity of the Divine essence, in which subsist three Persons. If Tertullian and Novatian use subordinationist language of the Son (perhaps borrowed from the East), it is of little consequence in comparison with their main doctrine, that there is one substance of the Father and of the Son. Callistus excommunicates equally those who deny the distinction of Persons, and those who refuse to assert the unity of substance. Pope Dionysius is shocked that his namesake did not use the word “consubstantial” – this is more than sixty years before Nicaea. At that great council a Western bishop has the first place, with two Roman priests, and the result of the discussion is that the Roman word “consubstantial” is imposed up on all. In the East the council is succeeded by a conspiracy of silence; the Orientals will not use the word. Even Alexandria, which had kept to the doctrine of Dionysius of Rome, is not convinced that the policy was good and Athanasius spends his life in fighting for Nicaea, yet rarely uses the crucial word. It takes half a century for the Easterns to digest it; and when they do so, they do not make the most of its meaning. It is curious how little interest even Athanasius shows in the Unity of the Trinity, which he scarcely mentions except when quoting the Dionysii; it is Didymus and the Cappadocians who word Trinitarian doctrine in the manner since consecrated by the centuries – three hypostases, one usia; but this is merely the conventional translation of the ancient Latin formula, though it was new to the East.
