These remarks of Fr. Samuel Edwards are worthy of some reflection:
The stage is now set for the consideration of the other major Pauline passage which relates to our topic, which begins at 2 Corinthians 10:11. Paul proceeds to ask a series of rhetorical questions which, taken together, give a fairly complete picture of what being in communion signified in the early Church: “Do not be mismated (heterozygountes) with unbelievers. For what partnership (metoche) have righteousness and iniquity? Or what communion (koinonia) has light with darkness? What concord (symphonesis) has Christ with Belial? Or what allotment (meris) has a believer with an unbeliever? What common ground (synkatathesis) has the temple of God with idols?” He then goes on, “For we are the temple of the living God; as God said, ‘I will live in them and move among them, and I will be their God, and they shall be my people. Therefore come out from them, and be separate from them, says the Lord, and touch nothing unclean; then I will welcome you, and I will be a father to you, and you shall be my sons and daughters, says the Lord Almighty.'”
The meaning of the six Greek words used here (heterozygountes, metoche, koinonia, symphonesis, meris, and synkatathesis) enable us to form a comprehensive definition of the meaning of communion. It is evident from a close examination of them what is the nature of the koinonia to which Paul refers. . . . It is a marital yoking, a partnership, which enables the participants to share in the life of God communicated through holy things and which stands on the common ground of doctrinal agreement and moral concord. The idea of a community not characterized by this shared standard of faith and moral order would rightly have been regarded as self-contradictory. A group of people who live together but have no common agreement on the nature of reality is not a community, but a voluntary aggregation of individuals formed for the pursuit of essentially individual purposes and ultimately held together only by self-interest or sentiment.
The participation or communion to which koinonia refers before all else is participation in Christ, particularly sacramental participation, communio in sacris, communion in holy things. Only in a secondary, derivative, and dependant sense does it refer to the fellowship or community between those who participate in holy things. Its primary reference is to participation in the life of Christ; participation in one another’s lives in a positive sense is possible only to the degree that we first participate in the life of Christ himself. Thus, the contemporary use of the notion of “community” to render this term, involves an inversion of the original priority of meaning.
In the New Testament, the sharing of communion always presupposes common faith. To demonstrate that this is not just a Pauline idea, we need only to turn to the first letter of John. Here he states that, “if we say we have communion (koinonia) with him and walk in the darkness, we lie and are not doing the truth; but if we walk in the light as he is in the light, then we have communion with one another and the blood of Jesus cleanses us from all sin.” (1:5-7)
Fr. Edwards expertly criticizes the present Protestant notion of communion (and notes its sources in nineteenth century German theology). It seems to me that Fr. Edwards is rightly debunking “lowest common denominator” ecumenism for the more meaty (and truthful) koinonia in the Person of Christ. And about that Person there are beliefs one must hold (and live) if one would be truly a follower of the Christ.