Person Supplants Substance as Meaning of Being
The God of the Bible is a God-in-relationship
“We observed that, in the ancient world, man could orient himself to God through knowledge and love but that any notion of a relationship between the eternal God and temporal man was regarded as absurd and hence impossible. The philosophical monotheism of the ancient world opened up a path for biblical faith in God and its religious monotheism, which seemed to facilitate once again the lost harmony between reason and religion. The Fathers, who started from the assumption of this harmony between philosophy and biblical revelation, realized that the one God of the Bible could be affirmed, in his identity, through two predicates: creation and revelation, creation and redemption. But these are both relational terms. Thus the God of the Bible is a God-in-relationship; and to that extent, in the essence of his identity, he is opposed to the self-enclosed God of philosophy.
“This is not the place to trace the complicated intellectual struggle that sought to establish the interrelatedness of reason and religion. It had followed from the idea of God’s unique oneness, yet now it was practically called into question once again. In the context of the present topic, all I will say is that, as a result of this struggle, a new philosophical category –the concept of `person’ – was fashioned, a concept that has become for us the fundamental concept of the analogy between God and man, the very center of philosophical thought.
Covenant as God’s Self-Revelation, `the radiance of his countenance’
“The meaning of an already existing category, that of `relation,’ was fundamentally changed. In the Aristotelian table of categories, relation belongs to the group of accidents that point to substance and are dependent on it; in God, therefore, there are no accidents. Through the Christian doctrine of the Trinity, relatio moves out of the substance-accident framework. Now God himself is described as a Trinitarian set of relations, as relatio subsistens. When we say that man is the image of God, it means that he is a being designed for relationship; it means that, in and through all his relationships, he seeks that relation which is the ground of his existence. In this context, covenant would be the response to man’s imaging of God; it would show us who we are and who God is. And for God, since he is entirely relationship, covenant would not be something external in history, apart from his being, but the manifestation of his self, the `radiance of his countenance.’”
[From "Many Religions - One Covenant," Ignatius (1999) 75-77]
 This is beautifully clear in C. Schonborn, “God’s Human Face: The Christ-Icon,” Ignatius (1994) 14-33.
 Even if the entire scope of the process is not yet clear, w can see the refashioning of the inherited categories in Augustine, De Trin. 5, 5, 6 (PL 42, 914): `Wherefore noting in Him is said in respect ot accident, since nothing is accidental to Him, and yet al that is said is not said according to substance… the [the Father and the Son] are so called, not according to substance, but according to relation, which relation, however, is not accident, because it is not changeable.’)