According to Joseph Ratzinger, the Greek notion of substance as the metaphysical rendering of “this God who had been understood as pure Being or pure thought, circling round for ever closed in upon itself without reaching over to man and his little world; this God of the philosophers, whose pure eternity and unchangeability had excluded any relation with the changeable and transitory,” is not helpful in accounting for the reality of the ontologically one God as a Trinity of Persons nor for Christ as Divine Person of two autonomous yet “compenetrating” natures. As he says elsewhere, “What may be a questionable idea in the context of physics was asserted by theology in the fourth and fifth century about the persons in God, namely, that they are nothing but the act of relativity toward each other. In God, person is the pure relativity of being turned toward the other; it does not lie on the level of substance – the substance is one – but on the level of dialogical reality, of relativity toward the other… Relation is here recognized as a third specific fundamental category between substance and accident, the two great categorical form of thought in Antiquity. Again we encounter the Christian newness of the personalistic idea in all its sharpness and clarity. The contribution offered by faith to human thought becomes especially clear and palpable here. It was faith that gave birth to this idea of pure act, of pure relativity, which does not lie on the level of substance and does not touch or divined substance; and it was faith that thereby brought the personal phenomenon into view.”
It should be noted here that Ratzinger sees this epistemological development that must take place in order to craft a metaphysics that will anchor relation as the prius in human thought as “a task that is still far from being accomplished.” This is precisely what he envisages as his principal task as Pope succeeding John Paul II and Vatican II: to move consciousness from a metaphysic of substance to a metaphysic of relation. And to that end, he published as his key-note statement: Deus Caritas Est. That is, God is an Actio that is Agape, the open Self-Transcendence that is a triple Self-Gift. “It thus becomes obvious … that the concept of God is removed from the realm of a mere ousia.”
Of course, the Fathers of the Church (Athanasius, in point) did not remove the Greek “substance,” ousia, from the account of the Being of God, but put it into a mysterious tension so that two of the divine Persons Who are irreducibly different as Father and Son (“The Father is greater than I,” [Jn. 14, 29]) are equal as Being but not the same Person.
At a much later date, Hegel notoriously remarked: “In my view, which can be justified only by the exposition of the system itself, everything turns on grasping and expressing the True, not only as Substance, but equally as Subject [Das Wahre nicht als Substanz, sondern eben so sehr als Subjekt]” An important commentator of Hegel, Nathan Rotenstreich, said: “If we take into account the religious background of Hegel’s thought, something else attracts our notice. At an early stage in Christian thought, subject acquired the meaning of person. In the history of Christian speculation about the Trinity, the notion of Person (Persona) arose as a kind of corrective to the notions of substance and the substantive unity of God. The notion of substance lacked personal character and could be viewed merely as essence, being or ousia.” 
Ingratitude Undermines Personhood
Not to be thankful is to arrogate the received being and goodness of self to self-achievement and self sufficiency. If personhood is to be in relation, and in the case of the Son of God, His very To Be as divine Person, equal in Being to the Father, then the very identity of the Son is to give glory to the Father in unending gratitude and glorification.
As images of God in the Son, the folkloric is telling with regard to the ontological constitution of the human person precisely because of its unreflective spontaneity. Lewis Hyde writes the following:
“Tribal peoples usually distinguish between gifts and capital. Commonly they have a law that repeats the sensibility implicit in the idea of an Indian gift. ‘One man’s gift,’ they say ‘must not be another man’s capital.’ Wendy James, a British social anthropologist, tells us that among the Uduk in northeast Africa, ‘any wealth transferred from one subclan to another, whether animals, grain or money, is in the nature of a gift, and should be consumed, and not invested for growth. If such transferred wealth is added to the subclan’s capital [cattle in this case] and kept for growth and investment, the subclan is regarded as being in an immoral relation of debt to the donors of the original gift.’ If a pair of goats received as a gift from another subclan is kept to breed or to buy cattle, ‘there will be general complaint that the so-and so’s are getting rich at someone else’s expense, behaving immorally by hoarding and investing gifts, and therefore eo being in a state of severe debt. It will be expected that they will soon suffer storm damage…’
“The goats in this example move from one clan to another… And what happens then? If the object is a gift, it keeps moving, which in this case means that the man who received the goats throws a big party and everyone gets fed. The goats needn’t be given back, but they surely can’t be set aside to produce milk or more goats. And a new note has been added: the feeling that if a gift is not treated as such, if one form of property is converted into another, something horrible will happen. In folk tales the person who tries to hold on to a gift usually dies; in this anecdote the risk is ‘storm damage.’ What happens in fact to most tribal groups is worse than storm damage. Where someone manages to commercialize a tribe’s gift relationships the social fabric of the group is invariably destroyed.”
Notice that the notion of "capital" is the existential and economic equivalent of "substance" that really is the subject that must be relational as gift. Notice how this speaks of the Christian anthropology at the basis of a true and healthy economic: that no one can keep anything for self. Private property is really the derivation of the achievement of self possession and self-identity, which results from the subduing of the earth - and which in reality is the self. Just as the self musts be given away, "capital" must always be available to the other as "labor." John Paul II remarked: "Isolating these means [of production] as a separate property in order to set it up in the form of 'capital' in opposition to 'labor' - and even to practice exploitation of labor - is contrary to the very nature of these means and their possession. They cannot be possessed against labor, they cannot even be possessed for possession's sake, because the only legitimate title to their possession -whether in the form of private ownership or in the form of public or collective ownership - is that they shoulde serve labor, and thus, by serving labor, that they should make possible the achievement of the first principle of this order, namely, the universal destination of goods and the right to common use of them" (Labor Exercens 14).
 J. Ratzinger, “Introduction to Christianity,” Ignatius (1990) 99.
 J. Ratzinger, “Journey Towards Easter” Crossroad (1987) 88-90; “Behold the Pierced One,” Ignatius (1986) 37-42; 92.
 J. Ratzinger, “The Notion of Person in Theology,” Communio 17 (Fall 1990) 444-445.
 J. Ratzinger, “Salvation and History” in “Section 2: Faith and History” in Principles of Catholic Theology” Ignatius (1987) 185.
 Ibid 185.
 Hegel, “Phenomenology of Spirit,” Preface.
 Nathan Rotenstreich, “From Substance to Subject,” Martinus Nijhoff, The Hague (1974) 2.
 Lewis Hyde, “The Gift,” Vintage Books (1983) 4-5.