The gift of the Holy Spirit at Pentecost “called all men into unity,” according to the Byzantine liturgical hymn of the day. Into this new unity, which St. Paul called the “body of Christ,” each individual Christian enters through baptism and chrismation (the Eastern counterpart of the Western confirmation) when the priest anoints the Christian with the words “the seal of the gift of the Holy Spirit.”

This gift, however, requires a person’s free response. Orthodox saints such as St. Seraphim of Sarov (1759–1833) described the entire content of Christian life as a “collection of the Holy Spirit.” The Holy Spirit is thus conceived as the main agent of humanity’s restoration to its original natural state through Communion in Christ’s body. This role of the Holy Spirit is reflected, very richly, in a variety of liturgical and sacramental acts. Every act of worship usually starts with a prayer addressed to the Holy Spirit, and all major sacraments begin with an invocation to the Holy Spirit. The eucharistic liturgies of the East attribute the ultimate mystery of Christ’s presence to a descent of the Holy Spirit upon the worshipping congregation and upon the eucharistic bread and wine. The significance of this invocation (in Greek epiklēsis) was violently debated between Greek and Latin Christians in the Middle Ages because the Roman canon of the mass lacked any reference to the Holy Spirit and was thus considered deficient by the Orthodox Greeks.

Since the first Council of Constantinople (381), which condemned the Pneumatomachians (“fighters against the Spirit”), no one in the Orthodox East has ever denied that the Spirit is not only a “gift” but also the giver—i.e., that he is the third person of the Trinity. The Greek Fathers saw in Genesis 1:2 a reference to the Spirit’s cooperation in the divine act of creation. The Spirit was also viewed as active in the “new creation” that occurred in the womb of the Virgin Mary when she became the mother of Christ (Luke 1:35); Pentecost was understood to be an anticipation of the “last days” (Acts 2:17) when, at the end of history, a universal communion with God will be achieved. Thus, all the decisive acts of God are accomplished “by the Father in the Son, through the Holy Spirit.”

The Holy Trinity

By the 4th century a polarity had developed between Eastern and Western Christians in their respective understandings of the Trinity. In the West God was understood primarily in terms of one essence (the Trinity of persons being conceived as an irrational truth found in revelation); in the East the tri-personality of God was understood as the primary fact of Christian experience. For most of the Eastern Fathers, it was not the Trinity that needed theological proof but rather God’s essential unity. The Cappadocian Fathers (St. Gregory of Nyssa, St. Gregory of Nazianzus, and St. Basil of Caesarea) were even accused of being tri-theists because of their conception of God as one essence in three hypostases (the Greek term hypostasis was the equivalent of the Latin substantia and designated a concrete reality). For Eastern theologians, this terminology was intended to designate the concrete New Testament revelation of the Son and the Holy Spirit as distinct from the Father.

Polarization of the Eastern and Western concepts of the Trinity is at the root of the Filioque dispute. The Latin word Filioque (“and from the Son”) was added to the Nicene Creed in Spain in the 6th century. By affirming that the Holy Spirit proceeds not only “from the Father” (as the original creed proclaimed) but also “from the Son,” the Spanish councils intended to condemn Arianism, which held that the Son was a created being. Later, however, the addition became an anti-Eastern battle cry, especially after Charlemagne, the Carolingian ruler of the Franks, was crowned emperor of the Romans in 800. The addition was finally accepted in Rome under Frankish pressure. It found justification in the framework of Western conceptions of the Trinity; the Father and the Son were viewed as one God in the act of “spiration” of the Spirit.

Byzantine theologians opposed the addition, first on the ground that the Western church had no right to change the text of an ecumenical creed unilaterally and, second, because the Filioque clause implied the reduction of the divine persons to mere relations (“the Father and the Son are two in relation to each other, but one in relation to the Spirit”). For the Greeks the Father alone is the origin of both the Son and the Holy Spirit. Patriarch Photius (9th century) was the first Orthodox theologian to explicitly spell out the Greek opposition to the Filioque concept, but the debate continued throughout the Middle Ages.

The transcendence of God

An important element in the Eastern Christian understanding of God is the notion that God, in his essence, is totally transcendent and unknowable. In this understanding, God can only be designated by negative attributes: it is possible to say what God is not, but it is impossible to say what God is. A purely negative, or “apophatic” theology—the only one applicable to the essence of God in the Orthodox view—does not lead to agnosticism, however, because God reveals himself personally—as Father, Son, and Holy Spirit—and also in his acts, or “energies.” Thus, true knowledge of God always includes three elements: religious awe; personal encounter; and participation in energies, which God freely bestows on creation.

This conception of God is connected with the personalistic understanding of the Trinity. It also led to the official confirmation by the Orthodox church of the theology of St. Gregory Palamas, the leader of Byzantine Hesychasts (monks devoted to divine quietness through prayer), at the councils of 1341 and 1351 in Constantinople. The councils confirmed a real distinction in God, between the unknowable essence and the energies which make possible a real communion with God. The deification of man, realized in Christ once and for all, is thus accomplished by a communion of divine energy with humanity in Christ’s glorified humanity.

Modern theological developments

Until the conquest of Constantinople by the Turks (1453), Byzantium was the unquestioned intellectual centre of the Orthodox church. Far from being monolithic, Byzantine theology was often polarized by a humanistic trend, favouring the use of Greek philosophy, and the more austere and mystical theology of monastic circles. The concern for preservation of Greek culture and for the political salvation of the empire led several prominent humanists to adopt a position favourable to union with the West. The most creative theologians (e.g., St. Symeon the New Theologian, died 1033; St. Gregory Palamas, died 1359; and Nicholas Cabasilas, died c. 1390), however, were found in the monastic party that continued the tradition of patristic spirituality based upon the theology of deification.

The 16th, 17th, and 18th centuries were the dark age of Orthodox theology. There was no opportunity for any independent theological creativity in any of the major regions of Orthodoxy—the Middle East, the Balkans, and Russia. With no access to formal theological education except in Western Roman Catholic or Protestant schools, the Orthodox tradition was preserved primarily through the liturgy, which retained its richness and often served as a substitute for formal schooling. Most doctrinal statements of this period, issued by councils or by individual theologians, were polemical documents directed against Western missionaries.

After the reforms of Peter the Great (died 1725), a theological school system was organized in Russia. Shaped originally in accordance with Western Latin models and staffed with Jesuit-trained Ukrainian personnel, this system developed in the 19th century into a fully independent and powerful tool of theological education. The Russian theological efflorescence of the 19th and 20th centuries produced many scholars, especially in historical theology—e.g., Philaret Drozdov, Vasily Osipovich Klyuchevsky, Vasily Vasilievich Bolotov, Evgeny Evstigneyevich Golubinsky, and Nikolay Nikanorovich Glubokovsky. Independently of the official theological schools, a number of laymen with secular training developed theological and philosophical traditions of their own and exercised a great influence on modern Orthodox theology—e.g., Alexey Stepanovich Khomyakov, Vladimir Sergeyevich Solovyev, and Nikolay Aleksandrovich Berdyayev. Others, such as Pavel Florensky and Sergey Nikolayevich Bulgakov, became priests. A large number of the Russian theological intelligentsia—e.g., Bulgakov and Georges Florovsky—emigrated to western Europe after the Russian Revolution (1917) and played a leading role in the ecumenical movement.

With the independence of the Balkans, theological schools were also created in Greece, Serbia, Bulgaria, and Romania. Modern Greek scholars contributed to the publication of important Byzantine ecclesiastical texts and produced standard theological textbooks. The Orthodox diaspora—the emigration from eastern Europe and the Middle East—in the 20th century contributed to modern theological development through their establishment of theological centres in western Europe and America.

Orthodox theologians reacted negatively to the new dogmas proclaimed by Pope Pius IX: the Immaculate Conception of Mary (1854), which held that Mary was conceived without sin, and papal infallibility (1870), which held that, under certain conditions, the pope cannot err when teaching on matters of faith and morals. In connection with the dogma of the Assumption of Mary, proclaimed by Pope Pius XII (1950), which held that Mary was raised to heaven in both body and soul, the objections mainly concerned the presentation of such a tradition in the form of a dogma.

In contrast to the trend toward social concerns evident in Western Christian thought since the late 20th century, Orthodox theologians have generally emphasized that the Christian faith is primarily a direct experience of the kingdom of God, sacramentally present in the church. Without denying that Christians have a social responsibility to the world, they consider this responsibility as an outcome of the life in Christ. This traditional position accounts for the remarkable survival of the Orthodox churches under the most contradictory and unfavourable of social conditions, but to Western eyes it often appears as a form of passive fatalism.