One can, of course, raise the question of how successful this effort was, but it cannot be denied that it was justified in its basic intention. The present work is intended to describe the main historical trends of Byzantine theology in close connection with its main theme, and the second part of this work is intended to show in a more systematic form that the results of Byzantine theological thought can also be presented as a synthesis. We intend not only to describe the idea of "deification" and its development in Greek patristic thought (there are many special studies on this subject), but to analyze the entire course of the historical development in Byzantium of theological ideas concerning the divine-human relations. Whether we are dealing with Trinitarian or Christological dogmas, whether we are investigating ecclesiology or sacramental teaching, the main current of Byzantine theology reveals to us the same vision of man called to "know" God, "to participate in His Life, to be 'saved' not only through the external action of God or through the rational knowledge of the truths proposed, but through 'becoming God'. And this theosis of man in Byzantine theology is radically different from the Neoplatonic return to the impersonal One: it is a new expression of the evangelical life "in Christ" and in the "communion of the Holy Spirit."

1. Chronological framework

There are good reasons to consider the historical period that followed the Council of Chalcedon (451) and the barbarian invasion of Italy to be Byzantine proper. The Council ended with the Monophysite schism, which tore Constantinople away from Alexandria and Antioch (ancient Eastern centers of theological creativity) and from the entire non-Greek East. In the meantime, among the Latins and the Greeks, despite the fact that they still belonged to the same Catholic, imperial Church, a sense of mutual alienation began to grow, so that the different trends in Christology, ecclesiology and pneumatology became more and more expressive in the context of the unparalleled cultural and intellectual superiority of Constantinople.

Historical circumstances thus placed Byzantium in an exceptional, excellent, and to some extent self-sufficient position, from which it developed a theological tradition that synthesized and at the same time creative.

For several centuries Byzantium would take a vital interest in restoring the unity of a disintegrating Christendom: faithful in its Christology to the Council of Chalcedon and the Tomos of Leo, it would preserve its bridges with the West in spite of all friction with it, and in keeping strictly faithful to the Alexandrian Christology of Athanasius and Cyril, it would also try, unfortunately unsuccessfully, to keep all doors open to the Monophysites.

These Christological commitments and debates imply a conception of the relationship between God and man, a theology of "participation" which, thanks to the creative synthesis of Maximus the Confessor, would serve as the backbone of the entire development of Byzantine Christian thought, up to the conquest of Constantinople by the Turks. Thus, there is an essential continuity between the patristic era and late Byzantine theology, as we intend to show in this study, and it embraces almost a whole millennium of Christian history in the East: from the Council of Chalcedon to the fall of Constantinople.

This continuity, however, does not manifest itself in any formal authority or model that would be recognized by everyone throughout the entire period indicated above. Rather, it consists in the consistency of the theological way of thinking, in the consistency of the understanding of human destiny in relation to God and the world. "God became man," writes Athanasius, "so that man could become God." This fundamental assertion of Alexandrian theology, which dominated all theological discourse on "deification," gave rise to many problems. Pantheism, flight from history, Platonic spiritualism carry obvious threats, and orthodox Chalcedonian theology as a whole is aware of them, implying a positive conception of man as a being called upon to constantly overcome his own created limitations. True human nature is not supposed to be "autocratic," but destined to participate in the divine life attainable in Christ. According to this concept, the purpose of man in the created world can be fulfilled only if the "image" of God, which originally constitutes part of human nature itself, is preserved without damage.

From the Christological controversies of the fifth century to the debates about the "essence" and "energy" of God that took place in the fourteenth century, all the major crises of Byzantine theological thought can be reduced to one or another aspect of this fundamental Christian question. Authors as diverse as Leontius of Jerusalem and Gregory Palamas, Maximus the Confessor and Symeon the New Theologian, Photius and Nicholas Cabasilas agree on the most basic points, as is easy to discover. It is this agreement that distinguishes Byzantine theology, considered as a whole, from the post-Augustinian and scholastic West, and therefore it becomes possible to attempt to offer a systematic exposition of Byzantine Christian thought, which we undertake in the second part of this work.

2. Living Tradition

It is very difficult to compose an exposition of this kind because of the very nature of Byzantine church life as reflected in theological literature. In the Byzantine era, as in the patristic era, neither councils nor theologians showed much interest in building positive theological systems. With very few exceptions, such as the Chalcedonian definition, the conciliar decrees themselves took the form of negations; they condemned the distortions of Christian Truth rather than tried to reveal its positive content – for it was perceived as a living Tradition and as an integral Truth, which is outside and above the doctrinal formula. Most theological writings are either exegetical or polemical, and in both cases the Christian faith is accepted as a given reality that can be interpreted or defended, but which does not need exhaustive formulations. Even John of Damascus, sometimes called "Aquinas of the East" for compiling a systematic "Exact Exposition of the Orthodox Faith" (De fide orthodoxa), in fact created only a brief manual, but not a theological system; and if his thought lacked something, it was precisely that originality of philosophical creativity, without which there is no new system.