John 17 is often sited for the cause of the ecumenical movements desire for reconciliation of “Christians”. It is true that Christ said these things but when the Scriptures are considered closely then it appears that the ecumenical movement has taken the words out of context.The unity that Christ desired in firstly grounded in Faith (John 17: 8-9) and in Himself, which also unites one into the Trinity (John 17:21-26). It is not a desire for all people to be united as an end in itself but all to be united in Himself. Those in Him are one because He is one. Thus unity is found not in humans agreeing with each other but in agreeing with Christ.
This agreement with Christ is through faith. This does not mean only the act of believing itself but also what one believes. One may be sincere and faithful in one’s belief but if one does not believe in Christ then such a belief is of no avail. Thus, union with Christ requires a union of faith, being of one mind and believing the same thing, the faith of Christ.
The Fathers of the Church summarised this Faith in the Creed, or the “Faith”. The Nicene-Constantinoplian Faith (as the Greek word for Creed is literally translated.) Thus, to accept the Faith of Christ and to be united to Him requires one to accept this Faith as it is without adding to it or subtracting from it. Unfortunately, the western Churches, added to this Faith and began to confess something different from the Faith of the Church. Eventually, when they showed themselves entrenched in the proclamation of this different Faith they became separated from Christ.
Being separated from Christ means separation from the Church and from the Holy Spirit. Even though those in many of these groups are referred to as “Christians” and their gathering/organisations are called “churches”, they are not properly so unless they are united to Christ, sharing one Faith with Him and with those whom also share this Faith. Because the Church on earth is the Incarnate presence of Christ, then it is seen in its physical presence that is linked through the laying on of hands, baptism and the Eucharist. Without the participation in these there is no participation in the Church. Those who have broken the physical connection with the Church must, along with accepting the Faith of the Church, also be physically reunited with the Church before being reunited with her. So, groups outside the Church cannot reunite with the Church by a mere confession of the Faith but they must each personally be physically brought back in the Church and established in the Church with a properly ordained Priest under a recognised Bishop.
On these grounds, the talk of reunion with those groups outside the Church, such as the various Protestant Churches, the Anglican Church and the Roman Catholic Church, is a mistaken, if it is based on a premise that these bodies are real Churches in Christ between whom there has somehow been a rift rather than a cutting off. Rather, it must be understood that a “reunion” of those other churches, also called “Christian churches”, can only come about not through an agreed declaration of faith that is acceptable to all within their present “traditions”, as if these are all different expressions of the one Tradition, but through repentance and the agreement with the Faith of the Church, abandoning their own “traditions” and accepting those of the Church. Each person so “reuniting” (“uniting” is a better term because almost all such persons have never been united personally to Christ, the Church) with the Church must be physically established in the Church through baptism, or perhaps at least the physical anointing of chrismation as an act of economy once they declare the Faith of the Church and renounce errors. There can be no corporate “reunion” because outside of Christ there is no true unity in a church but rather a collection of individuals. Only in Christ is the Church truly united and one body.
So, God does desire union, but in Himself, in Christ and in His faith, in accepting His words. Christ prays for those accepting His words and not for the world. Those bodies separated from the Church are not churches in the true sense of the word and Christ does not desire the union of such groups as an end in itself but rather repentance and coming to Him to be united to the Church. There is a requirement for the Church to accept those who desire to repent but none to unite with other groups who claim to be Christian and even hold many of the same beliefs. Rather it is to speak the truth clearly in love to keep open the way for repentance, while rejecting those who refuse to repent of error as sons of perdition because in this state they are indeed bound for eternal perdition being apart from Christ; it isn’t “nice” but it is the reality. Christ’s love requires that the errors need to be identified in discussions and the truth made clear to allow repentance. Identifying common areas of faith helps to ground teaching of understanding towards the truth but it is the errors that have caused the division and these need to be constantly noted and shown for what they are. One must accept what the Church, Christ, accepts and reject what the Church, Christ, rejects. Again, it is of no avail to accept what the Church accepts but fail to reject what she rejects, that is leaving those groups persisting in error and joining the Church, the pillar of the Truth.