The four marks of the Church are set forth in the Ninth Article of the Nicene-Constantinopolean Creed. The Church is “One, Holy, Catholic, and Apostolic.” Each of these attributes is necessary to a proper and full description of the true Church. Any group lacking even one of these characteristics is, by definition, not the Church.
The first attribute of the Church is that it is One; it is undivided. Christ’s design for the Church as One, is shown in his prayer in John 17, where he asks “Holy Father, keep through thine own name those whom thou hast given me, that they may be one, as we are.” This was well understood by the post-Apostolic fathers, as well. “The Church, having received this preaching and this faith, although she is disseminated throughout the whole world, yet guarded it, as if she occupied but one house. She likewise believes these things just as if she had but one soul and one and the same heart and harmoniously she proclaims them and teaches them and hands them down, as if she possessed but one mouth. For, while the languages of the world are diverse, nevertheless, the authority of the Tradition is one and the same.” (St. Irenaeus, Against Heresies 1, 10, 2). Likewise, St. Cyprian warns “Who, then, is so wicked and faithless, who is so insane with the madness of discord, as to believe that the unity of God can be divided, or to dare to tear the garment of the Lord, the Church of Christ? He himself warns us in his Gospel, “There shall be one flock and one shepherd.” (<em>The Unity of the Church, </em><em>ch. 10,</em><em> </em>citing John 10:16). This unity is expressed both inwardly, through sharing in the Holy Mysteries, and outwardly through the common worship of the faithful. It is a unity both visible in the adherents and invisible through the presence of Christ and the Holy Spirit. The fact that some have fallen away or been cast out of the Church does not disturb the Unity of the Church, for those outside the Church are not the Church. They may call themselves Christian, and may claim to be a church, but if they do not hold to the Orthodox teaching, they cannot be the Church. There is but One true Church and it is the Orthodox Church which preserves that deposit of the Faith once delivered to the apostles.
The second mark of the Church is that it is Holy. By Holy, we mean that the Church has been sanctified by Christ. The Church is Holy because it’s head is Christ. It is Holy because it contains the Grace of the Holy Spirit. It is present in the Mysteries, in the teaching and in the sanctification of the Saints. The Holiness of the Church is attested in Scripture. St. Paul writes to the Ephesians, “Husbands, love your wives, even as Christ also loved the church, and gave himself for it;That he might sanctify and cleanse it with the washing of water by the word, That he might present it to himself a glorious church, not having spot, or wrinkle, or any such thing; but that it should be holy and without blemish. (Ephesians 5:25-27).
The third mark of the Church is that it is Catholic. The use of the word Catholic describes universality of a Church that encompasses all with its fullness. As St. Paul wrote to the Ephesians, “He put all things in subjection under His feet, and gave Him as head over all things to the church, 23which is His body, the fullness of Him who fills all in all.” (Ephesians 1:23). The Church did not grow or evolve to catholicity. Rather, the fullness of the Church was present even on the day of Pentecost when the Church was born. The Church’s catholicity is represented in many ways. All are called to salvation (and hence membership in the Church). The Church is not confined or limited by place or time, nor by reference to any civil structure. The fathers of the Church consistently refer to the Church as Catholic. St. Cyprian says “the Church which is Catholic and one, is not cut nor divided, but is indeed connected and bound together by the cement of priests who cohere with one another.” (Letters 66). Likewise, the Ecumenical Councils repeatedly describe the Church as Catholic. (see e.g., Canons VIII and IX, First Ecumenical Council, Canon XIV, Fourth Ecumenical Council).
Finally, the Church is also Apostolic. This is true in several senses. Obviously, the Apostles were present when Christ appeared resurrected. This witness, their preaching and sufferings mark the beginning of the Church. Likewise, they preserved the teaching of Christ and established the Holy Tradition of the Church both by their words and their examples. In addition, they established and performed the sacraments of the Church as Christ had commanded. The Apostolic nature of the Church also refers to the means of succession of the Apostles. The first Bishops of the Church were appointed by the Apostles, and their successors have continued this unbroken chain of Apostolic succession. As the Church grew, the Bishops appointed deacons and presbytyrs to perform the mysteries in succession of them. Apostolic succession was considered an absolute requirement in the early Church. “It is necessary to obey those who are the presbyters in the Church, those who, as we have shown, have succession from the Apostles; those who have received, with the succession of the episcopate, the sure charism of truth according to the good pleasure of the Father. But the rest, who have no part in the primitive succession and assemble wheresoever they will, must be held in suspicion” (Irenaeus, Against Heresies 4:26:2). In addition to appointing successors, establishing order in the Church was also a function of the Apostles. (1 Cor. 14:40). “The [Apostle John] came back again to Ephesus from the Island of Patmos; and, upon being invited, he went even to the neighboring cities of the pagans, here to appoint bishops, there to set in order whole Churches, and there to ordain to the clerical estate such as were designated by the Spirit. (Clement of Alexandria, Who is the Rich Man that is Saved?, 42:2).
In both Scripture and the witness of the early fathers, the nature of the Church as One, Holy, Catholic and Apostolic is clearly confirmed. These intrinsic marks of the Church may be used to test any group that claims to be the Church. In the absence of these distinctives, the group cannot be the Church. However, we must still be careful, as even a group claiming these marks may not confess the Orthodox faith. If the confession is lacking, the group is assuredly outside of the Church.