As we mentioned in the section on methodology, the approach that characterizes the research and studies of John Zizioulas in systematic theology is that of the ontological hermeneutics of faith and the doctrines of the Church. In his attempt to interpret the doctrines of faith ontologically, to consider them as answers to the fundamental existential questions of man, Zizioulas has focused his studies more thoroughly on the following topics:

a) In the relationship between Hellenism and Christianity as a source and means of interpretive understanding of the Christian faith. Orthodoxy, especially Dogmatic, cannot be understood without a deep knowledge of the way in which the Greek spirit assimilated the preaching of the Gospel. The meeting of the Gospel, which was initially characterized by the Semitic-Jewish mentality, and historically appeared for the first time in a non-Greek area with Greek thought, was not an easy and simple task. An extensive study by Zizioulas in the History of the Greek Nation (vol. VI, published by Athens Publishing House) attempts to demonstrate how the ontological question, which has always occupied Greek thought, as well as the related cosmological interest, were combined with the Biblical spirit, which was more historically oriented than ontologically and cosmologically oriented. The position developed by Zizioulas was that the thought of the Greek Fathers, especially the Cappadocians and Saint Maximus the Confessor, managed to creatively synthesize the interest in history with that in ontology, and from this synthesis came the whole theological edifice of Greek Orthodoxy.

b) In the concept of truth, one of the consequences of the creative synthesis between the Biblical and Greek spirit, as it was finally shaped in the Greek Patristic thought. In his extensive special study (“Truth and Communion”), as well as in his other doctrinal studies, Zizioulas attempts to demonstrate that in Orthodox patristic thought, the concept of truth is related to ontology, history (and related eschatology), as well as to the concept of κοινωνίας (communion), i.e., the concept of relationship and community.

The importance of this position, which has already been pointed out by commentators of Zizioulas’ work, is multifaceted. In particular, it demonstrates that:

(i) The Greek patristic theology and the Orthodox systematic theology consistent with it possess all the conditions to converse and meet spiritually with the modern post-Einstein natural science and its philosophical extensions. The search for truth in the inseparable relationship between space and time, essence and event, thus emerges as a common ground of theology and natural science. According to Zizioulas, there are not “two” truths (religious or theological and scientific), but one truth for both theology and science. The consequences of this position can, and must, with an appropriate creative approach to theology and positive sciences, prove to be of enormous importance and significance. Toward this direction, he especially saw, along with God, the continuation of his efforts in the field of systematic theology.

(ii) The concept of truth cannot be isolated from its social content. The inextricable connection between truth and society, which Zizioulas’ work highlights, demonstrates that theological and sociological truth cannot but eventually coincide, even if in a dialectical form. If truth is a matter of relation, not only of space and time (cosmological, “physical” truth) but also of persons, then systematic theology clearly has substantial sociological ramifications. This leads to the next point of Zizioulas’ contribution.

c) Contribution to the understanding of the concept of person. One of the most basic consequences of the ontological hermeneutic method of systematic theology was, in his work, the importance of Christian doctrinal theology for the concept of the person. In his extensive studies, he first tried to demonstrate that the concept of the person as a hypostasis, i.e., as an absolute and primary ontological category, was born in the area of Greek Patristic thought and, in fact, as a result of the synthesis of the ancient Greek interest in ontology with the social-community and historical approach to the truth from the Biblical spirit, in the context of the effort of the Greek Fathers of the Church, especially the Cappadocians, to formulate the doctrine of the Holy Trinity. In this effort, a true philosophical revolution took place with the identification of two terms, which were previously incompatible in philosophy, that is, the terms “person” and “hypostasis.” This identification, made by the Cappadocian fathers in order to avoid Sabellianism in the doctrine of the Holy Trinity, meant for the first time that a category, which basically denotes “relationship,” acquires the content and meaning of “hypostasis,” i.e., becomes a primary ontological category. We have a transition from the concept of the person as a mask, to that of the person as a hypostasis, as an absolute, unique, complete, unrepeatable, and irreplaceable identity.

The definition of the concept of person that Zizioulas gave in this way stems from the patristic theology of the Holy Trinity, according to which the being of God is “hypostasized,” that is, exists, by the persons of the Trinity with a first ontological “cause” the person of the Father. That is, God does not exist first as an essence, and then—logically, always—as a person, as Western theology believes from Saint Augustine onwards. The concept and truth of the persons is a primary and not a secondary ontological category for the being of God. For this reason, the doctrine of the Holy Trinity should not follow that of On the One God, as is the case with Western influence in Dogmatics, even of Orthodox, and theologians of recent times.

Using the concept of the person as a primary theological category allows systematic theology to intervene in modern Western Personalism and expose its weaknesses, thus demonstrating the importance of theology for social philosophy, sociology, and the humanities in general. The fact that the above positions of John Zizioulas are the subject of discussion in areas broader than theology demonstrates the legitimacy that the approach, which characterizes his effort in systematic theology, can have for the humanistic sciences in general.