Are the Heterodox Members of the Orthodox Church?
Firstly, it is necessary to clarify that as Orthodox Christians we believe, in agreement with the Symbol of Faith (the Creed) of Nicene-Constantinople (381 AD), “in One, Holy, Catholic, and Apostolic Church”. According to the unbroken dogmatic consciousness of the Orthodox Church throughout the ages, i.e., according to her self-consciousness, this One Church is the Orthodox Church.
The confession of the Symbol that the Church is “One” means that this is the basic attribute of her self-identity. In practical terms this means that the Church is not able to be divided – to be split apart – because this is the Mystical Body of Christ. Christ as the Head of the Body of the Church is neither able to have many bodies, nor to possess a divided one. In the Body of Christ even death itself is defeated. As such, whoever is placed within this Body also remains alive in it by the divinely-working mystery: the keeping with love of the commandments. They pass over from biological death to the eternal and everlasting life of the Triadic God. Just as the branches of the vine are not able to live and to bear fruit if they are cut-off from the vine, so also the believer – or even entire communities of believers, regardless of their numbers – who are cut-off from the Church, are not able to exist in Christ, nor to introduce another Church [into existence].
The faith of the Church is inspired by God and non-negotiable. In agreement with Her clear faith, many divided churches are not able to exist since ‘one’ and ‘many’, or ‘one’ and ‘divided’, is a contradiction in terms. ‘Divided’ refutes, in practice, faith in the reality of the Church, which based on its own Orthodox self-consciousness is only able to be understood as ‘one and undivided’. When someone consciously speaks about a divided Church, it constitutes a denial of the Faith of the Church, a denial of Her self-identity and self-consciousness. As such, Orthodox Christians do not have any psychological self-identity complex as a result of the breaking-off of Western Christians from the Body of the Church. Certainly, though, the Orthodox do grieve, pray, and are interested in their repentance and return.
1. Apostolic Faith
The incorporation and remaining in the Mystical Body of Christ, the Church, is not unconditional. It presupposes, at any rate, the acceptance – with conditions – and confession of the Apostolic Faith, just as it is defined and established by the decisions of the Ecumenical Synods of the Church.
As such, when a believer (regardless of the institutional position that he holds in the Body of the Church), or a group of believers (regardless of their numbers violate on principle the established faith of the Church, they are cut-off from Her Body. They are defrocked, whatever priestly rank they possess, while laymen are excommunicated, as is evident from the decisions of the Ecumenical Synods. This means that they are not able in the future to partake and to commune in the Mysteries (sacraments) of the Church.
The Roman Catholics have officially fallen away from the Church in the 11th century. In 1014, they introduced into the Symbol of Faith their erroneous dogmatic teaching about the Holy Spirit: the well-known Filioque. According to this teaching the Holy Spirit as Divine Person has his procession both from the Father and from the Son. The dogmatic teaching of the Roman Catholics, however, overturns the Apostolic Faith of the Church in the Triadic God, since according to the Evangelist John the Spirit of Truth “proceeds from the Father” (John 15:26). Moreover, the 3rd Ecumenical Synod through its president St. Cyril of Alexandria, concerning the Symbol of Faith determined prohibitively that “οὐδενί ἐπιτρέπεται λέξιν ἀμεῖψαι τῶν ἐγκειμένων ἐκεῖσε ἤ μίαν γοῦν παραβῆναι συλλαβήν” (“It is not permitted to anyone to add or to subtract even one syllable” from these which were set forth in the Symbol of Faith). All the subsequent Ecumenical Synods accepted the decisions of this 3rd Ecumenical Synod.
It is evident, then, that the Roman Catholics – and by extension the Protestants who adopted the Filioque – have fallen away from the Apostolic Faith of the Church. It is because of this, not to mention all the subsequent innovations in the Faith on the part of Western Christianity (such as the Infallibility of the Pope, the Mariological dogmas, Primacy of the Pope, Created Grace, etc.) that these have fallen away.
2. Apostolic Succession
With the Apostolic Faith is also inseparably joined Apostolic Succession. Apostolic Succession only possesses true substance within the Body of the Church, and it presupposes moreover the Apostolic Faith.
When we speak of Apostolic Succession we mean the unbroken succession of the leadership of the Church from the Apostles. This continuation has a charismatic character and is secured by the transmission of the spiritual authority of the Apostles to the Bishops of the Church, and through them to the priests.
The manner of transmission of the spiritual-apostolic authority to the Bishops happens by consecration (xeirotonia). If, then, some bishop has received his consecration in the canonical-ecclesiastical manner and subsequently is found outside the Church because of his erroneous belief, he in essence stops possessing Apostolic Succession as well – since this succession only has meaning within the Mystical Body of Christ, the Church.
Consequently, if some bishop or entire local Church – regardless of the number of its members – falls away from the Faith of the Church, they cease having Apostolic Succession, just as was expressed infallibly in the Ecumenical Synods, because they are already found outside of the Church. And since Apostolic Succession is in essence  broken, it is not possible to speak about the possession or continuation of this succession for those who have fallen away from the Church.
On the basis of the above, the Pope himself – as also the entirety of the Roman Catholic bishops – is devoid of Apostolic Succession, since being devoid of the Apostolic Faith, they have fallen away from the Church. Speaking about Apostolic Succession outside of the Church, therefore, is an unsubstantiated scholarly discussion – that is to say, a discussion not based in theology.
3. Priesthood and the Other Mysteries
The priesthood in the context of the Church is the priesthood of Christ, since Christ himself perfects the Mysteries of the Church through His Bishops and Priests.
The priesthood presupposes its uninterrupted continuation from the Apostles. That is to say, it presupposes Apostolic Succession. Primarily, though, it presupposes the God-Man Christ as officiant in His Mystical Body, the Church. In the final analysis, the priesthood of Christ exists in the Church and is provided by Christ Himself through the Church and for the Church. An autonomous priesthood and Mysteries (sacraments) autonomous from the Church are not able to exist.
The priesthood – just as for that matter, all the Mysteries also – is a liturgical manifestation of the Church (the Church “is marked by the Mysteries” according to St. Nicholas Kavasilas). This means that in order for the Mysteries to exist, the Church must exist first. The Mysteries are like branches of a tree; living branches that bloom and bear fruit are able to exist only when these are organic extensions of the tree, i.e., when they are ontologically connected with the trunk of the tree.
It is theologically incomprehensible to maintain that the heterodox Roman Catholics and Protestants have even one Mystery, e.g., baptism. The fundamental question that must be raised here is: Who officiates the Mystery of Baptism? From where does the officiant find his priesthood? Who gave him the priesthood since this exists only within the Church? And where did the heterodox find the Church, since they, because of their erroneous dogmas of faith, fell away from Her?
4. The Theory of the “Two Lungs” of Christ
This theory has its origins in Roman Catholicism. According to this theory, Christ has as His “lungs” Roman Catholicism and the Orthodox Church.
Today, unfortunately, this theory has also been adopted rather uncritically by many Orthodox hierarchs and lay-academic theologians. And we say ‘uncritically’ because this theory, judged from an Orthodox perspective, is not only theologically unsound, but also blasphemy strictly speaking.
The Orthodox Church is differentiated ontologically from Roman Catholicism for purely dogmatic reasons. As such, the Orthodox Church considers that only She preserves the character of the Church as the Theanthropic Body of Christ. Roman Catholicism fell away from the Church of Christ a thousand years ago.
In addition, since the Church according to the Symbol of Faith is “One” and united, it is – theologically speaking – completely incomprehensible to understand, in agreement with the above theory, that Orthodoxy and Roman Catholicism are the “two lungs” of Christ, and equal members of the Body of Christ. In this case we are forced to hold that the other members of the Body of Christ either remain unaccounted for ecclesiologically,or are ecclesiologically made up from other churches – outside of the two [Orthodoxy and Roman Catholicism]. Such a view, however, will lead us straight to the adoption of the Protestant ecclesiology of the “Branch Theory”.
[When we say the “Branch Theory”, we mean the theory of the Protestants about the identity of the Church. The Church according to them is the invisible communion of the saints. All the dogmas of the different historical-empirical churches possess legitimacy and equality of existence, as branches of the one tree of the invisible church. The invisible church is the real church, which church is confessed in the Symbol of Faith. Consequently, no portion of the local church of whatever dogmatic confession embodies the “One, Holy, Catholic, and Apostolic Church”. No local church is able to assert that she possesses the fullness of the revealed truth. The church of Christ is the total sum of her apportioned parts, i.e., all local churches of all dogmatic confessions no matter how they differ dogmatically between one another.]This is completely unacceptable from an Orthodox perspective.
Of Roman Catholic origin, the aforementioned theory concerning the “two lungs” of Christ is blasphemy when it is adopted by Orthodox Christians. Strictly speaking, it is blasphemy because it places within the immaculate Body of Christ Roman Catholicism as His organic members (as one of His “lungs”). And this is done at the same time that Roman Catholicism, in actuality, suffers both officially and ontologically as being outside of the Theanthropic Body of the Church.
5. “Sister Churches”
To begin, the term “sister churches” [as a term] can be viewed as indifferent to unacceptable. It is theologically indifferent when it is used in order to describe the relationship between local Orthodox Churches. But the term is theologically unacceptable when it is used to define the ontological character of the Orthodox Church and of Roman Catholicism.
First of all, the term “sister churches” is not biblically founded, nor even justified. When the Apostle Paul mentions different local Churches, he doesn’t call them “sisters”, nor does he mean that there exists some Church as “mother” of these local Churches. He possesses an awareness that the Church is “One” and that she has a universal character with the concept of the fullness of her truth and life, the head of which – as we have said – is Christ Himself. So when [St. Paul] addresses himself to a local Church, he has the characteristic expression: “To the Church which is in… (e.g. Corinth)”. This means that the manifestation of the entire Church is able to occur in each place wherever the Eucharistic community of the faithful under its Bishop exists. It is certainly self-evident that the unity of these local Churches is held fast by the communion between them in this faith, life, and ecclesiastic order. The synod of their Bishops guarantees in practice the unity of the local Churches.
From the above it becomes clear that since even like-minded local Churches within the bounds of Orthodoxy are not theologically justified in being called “sisters”, much more is there no theological-ecclesiological grounds for calling the Orthodox Church and Roman Catholicism “sister churches”. Furthermore, Roman Catholicism is not strictly speaking able to be called the Church after 1014 A.D. since from then the disciplinary proscriptions of the Ecumenical Synods were spiritually in force for them as a result of their fall from the Theanthropic Body [of the Church].
Here it is necessary to note that the lifting of the above disciplinary proscriptions is not able to take place simply by any official personage of the Church – however highly he is found in the ecclesiastical hierarchy; these can only be lifted by an Ecumenical Synod. But even this can only happen in the event that beforehand the dogmatic teachings are rejected which resulted in Roman Catholicism’s fall from the Church [in the first place].
And so it is clear that officially from 1014 A.D., Roman Catholicism is not the Church. This means practically speaking that it does not have the correct Apostolic Faith or Apostolic Succession. It does not possess Uncreated Grace, and by extension does not have the divine-working Mysteries that render the Theanthropic Body of the Church, the “communion of theosis” of mankind. And so since the Church is not able not to be and remain “One” and “undivided” until the end of time, each Christian community outside of the Orthodox Church is simply heretical.
(Translated from the Greek by: Matthew Penney)
(This paper was originally published in «Οικουμενισμός: Ιστορική και Κριτική Προσέγγιση», Συνείδησι (εκτάκτη έκδοση της Ι.Μ. Μετεώρου, Αγία Μετεώρα), June 2009, p. 78-83. [An English rendering of the title is: “Ecumenism: A Historical and Critical Approach”, Syneidisi (Special Publication of the Holy Monastery of Meteora)]. )
 [T.N.] ‘Charismatic’ in an Orthodox sense should be understood generally as referring to a ‘charism’ – gift from God. It should not be confused with, or limited to, the various “charismatic” phenomena observed within the “Charismatic movements” of Protestantism and Roman Catholicism.
 ουσιαστικά (ousiastika): “in essence” or “essentially”. The meaning above seems to correspond to “in actuality” or “in fact” based on its context.
 Literally ‘penances’.
(Source: by Dr. Demetrios Tselengidis, professor at Aristotle University in Thessaloniki, Greece; http://www.impantokratoros.gr/members-church-heterodox.en.aspx)