We find upon all occasions, the early Christian writers speak of the Father as superior to the Son, and in general they give him the title of God, as distinguished from the Son; and sometimes they expressly call him, exclusively of the Son, the only true God; a phraseology which does not at all accord with the idea of the perfect equality of all the persons in the Trinity. But it might well be expected, that the advances to the present doctrine of the Trinity should be gradual and slow. It was, indeed, some centuries before it was completely formed.
Part I : The History of Opinions Relating to Jesus Christ, § III : The Supremacy was always ascribed to the Father before the Council Of Nice - An History of the Corruptions of Christianity (1782)