The being of God is a relational being: without the concept of communion it would not be possible to speak of the being of God. The tautology "God is God" says nothing about ontology, just as the logical affirmation A = A is a dead logic and consequently a denial of being which is life. It would be unthinkable to speak of the "one God" before speaking of the God who is "communion," that is to say, of the Holy Trinity. The Holy Trinity is a primordial ontological concept and not a notion which is added to the divine substance or rather which follows it [...]. The substance of God, "God," has no ontological content, no true being, apart from communion. Communion is not a relationship understood for its own sake, an existential structure which supplants "nature" or "substance" in its primordial ontological role—something reminiscent of the structure of existence met in the thought of Martin Buber. Just like "substance," "communion" does not exist by itself: it is the Father who is the "cause" of it. This thesis of the Cappadocians that introduced the concept of "cause" into the being of God assumed an incalculable importance. For it meant that the ultimate ontological category which makes something really be, is neither an impersonal and incommunicable "substance," nor a structure of communion existing by itself or imposed by necessity, but rather the person. The fact that God owes His existence to the Father, that is to a person, means (a) that His "substance," His being, does not constrain Him (God does not exist because He cannot but exist), and (b) that communion is not a constraining structure for His existence (God is not in communion, does not love, because He cannot but be in communion and love). The fact that God exists because of the Father shows that His existence, his being is the consequence of a free person; which means, in the last analysis, that not only communion but also freedom, the free person, constitutes true being. True being comes only from the free person, from the person who loves freely—that is, who freely affirms his being, his identity, by means of an event of communion with other persons.
John Zizioulas, Being and Communion.













