According to Orthodox ecclesiology, the terms “Church” and “Orthodoxy” have the same meaning.  The Church is definitely Orthodox, and Orthodoxy is the One, Holy, Catholic (overall) and Apostolic Church – the Body of Christ.  Given that Christ is only one, the Church can therefore only be one.  This is why there can be no notion of “division” within the Church.  There can only be a departure from the Church.  Thus, during certain historical moments, heretics and schismatics were “cut off” from the one body of the Church and were no longer members of its body.

            The Church possesses the totality of the Truth; not an abstract kind of truth, but a way of life that saves mankind from death and makes him “God by Grace”. In the opposite case, heresy constitutes a partial or a full denial of the Truth; it is a shattering of the Truth, which takes on the form and the pathology of a mere ideology. It distances mankind from the way of living that God gave to His Church, and it causes it to die spiritually.

            Furthermore, the dogmas, which enfold the transcendental truths of our faith, are not just a series of abstract meanings and intellectual concepts, nor are they –even more so- a form of medieval obscurism or a theological scholasticism. They are the expressions of the experience and the way of life of the Church.  This is why, when there is a difference in dogmas, there is most certainly a difference in one’s way of life.  Whomsoever underestimates the precision involved in faith, cannot live the fullness of life in Christ.

            A Christian has to accept everything that was revealed by Christ; not any kind of  “minimum”, but everything.  Because it is only in the totality and the integrity of the faith that the catholicity (“overallness”) and orthodoxy of the Church are preserved.

           This is the explanation for the “to-the-death” struggles of the holy Fathers for the preservation of the Church’s faith, and their meticulous attention to the formulation –with the enlightenment of the Holy Spirit- of the “terms” arising from each Ecumenical Synod (council).  These “terms” signify nothing more than the boundaries and the borders of the Truth, so that the faithful would be able to discern between the Church as Orthodoxy, and a heresy.

            By denying the totality of the Truth, the heterodox distanced themselves from the Church. That is the reason they are heretics. They have consequently deprived themselves of the sanctifying grace of the Holy Spirit and their “sacraments” have no validity. Therefore, the baptism “sacrament” that they perform does not have the prerequisites to embody them into the Body of Christ.

            According to the 68^th Canon of the Holy Apostles, “….for it is not possible to accept, either as faithful or as clergymen, those who have been baptized or ordained by heretics…” (Τους γαρ παρά των αιρετικών βαπτισθέντας ή χειροτονηθέντας ούτε πιστούς ούτε κληρικούς είναι δυνατόν). Saint Nicodemus of the Holy Mountain supplements the above, by saying that “The baptism of all the heretics is irreverent and blasphemous, and has nothing in common whatsoever with that of the Orthodox”. (’Όλων των αιρετικών το βάπτισμα είναι ασεβές και βλάσφημον και ουδεμία κοινωνίαν έχει προς το των Ορθοδόξων).