Whether in heaven or on earth, the Head of the Church is Christ Himself, the New Testament teaches. All breath and life come together as one because Christ is the only breathing One who can give life to a body. All Christians are unified into the sacraments through baptism, Eucharist, and the Spirit of Christ. In Holy Tradition and Scripture, the signs of unity are not merely outward nor merely inward; the body and spirit in a great mystery are one. God made the Church one so that mankind cannot undone this teaching on unity. This oneness is “ancient,” teaches Clement of Alexandria, because it is tied to the One God, the Father, the Son, and the Holy Spirit. Because of that, the Old and New Testaments are really One Testament that stretches across time, as he writes in the Stromata.
In the Eastern churches, unity was taught to founded on the existence of the Holy Trinity and how the Church can imitate that divine unity in “openness and love.” There is, then, only “one mind” among Christians and the true Church. The Eucharist has been the sign of unity and the way Christians are unified by partaking of the holy communion. St. Cyril of Alexandria teaches that “for if we partake of the one Bread, we are all made one Body; Christ cannot suffer severance.” Because of the communion of Christ’s Precious Body and Blood, we also have unity with the Holy Spirit. The Church’s oneness and the so often talked about unity of Christians today comes from the oneness of the Holy Trinity.
The Holy Trinity established the episcopate to help us order our lives and arrange ourselves to live within the sacraments. In the East, Christians who have separated themselves from the Church were dealt with according to the degree of deviation from dogmas and to the degree of schism. If the separation was serious and involved dogmatic variance with the teachings on the Trinity, akrivia or strictness might be used by the bishops. Heretics who doubted foundational dogmas had to be baptized in order to enter the Church, for example. If the separation was less about doctrines but involving a minor schism or dispute over ecclesial territory or historical misunderstandings, then economia or a lenient approach might be used. Schismatic groups who were already baptized in the Trinity, for example, and desired to enter the Church, did not need to be re-baptized, as St. Augustine and the East argued. St. Cyprian of Carthage also started with the Holy Trinity as the foundation of the Church, but with an emphasis on St. Peter as representative of the unity of all bishops in the Church, since his main argument with the schismatic Novatians set up rival bishops in opposition to the bishop of Rome. In both eastern and western churches, the One, Holy, Catholic and Apostolic Church was found in the one episcopate with its “starting-point” in St. Peter; however, Rome developed a theology that connected this idea specifically with the Roman throne later. In the West, there was a tendency to apply definitions of outlining the effects or powers, effectus as St. Augustine called it, and degrees of grace in schismatic groups. Both East and West did not view the sacraments of those who separated themselves as effectual to change the lives of Christians, but that those sacraments offered outside the Church can be “perfected” when they are brought under the unified episcopacy. The lamb must be eaten within the house at the exodus just as holy communion can only be received within the Orthodox Church. Spiritual unity of sacraments is arranged orderly and kept organized by the episcopate to help Christians maintain “one mind” within the altars of their heart just as priests offer sacrifice on the altar during the liturgy to make us all holy. The next chapter discusses, then, the holiness of the Church.