A church gathers; but it exists apart from these gatherings. It could not exist without them, but because they do happen, a church is more than them. Something exists through these gatherings. That something is a community.

This idea is expressed in rich and diverse ways in the Bible. In Ephesians 2:11–22, the reconciliation of Jews and Gentiles in Christ prompts Paul to use a series of rich descriptions of the social significance of what has taken place. Paul speaks of “one new humanity” (verse 15), reconciled in peace (17) on the basis of shared access (18). The gentiles are “fellow citizens” and “members of the household of God” (19, cf. 12), part of a temple of God in the Spirit (20–22). Here, as elsewhere, it is hard to avoid the conclusion that what is spoken of is more than a meeting. It is a community that is brought into existence, a “fellowship” (koinônia) of Jesus (1 Cor 1:9), a “household” of God (Gal 6:10), a “brotherhood” (1 Pet 2:17).
What, though, is a community? Oliver O’Donovan puts it this way:
“Community” means a sphere in which things are held in common rather than in private, as “ours” rather than “yours” or “mine.” The essence of community is “communication,” the exercise of sharing things or transmitting them among two or more people… Those who are partners to communication form a community. They become a “we” in relation to the object, whatever it is, that is common to them. (Common Objects of Love, 26–27)
That “object” is Christ, through His Spirit. This is what we share (cf. Phil 2:1), and therefore what binds us together. Saint Augustine described it like this:
The children of grace… form a community where there is no love of a will that is personal and, as we may say, private, but a love that rejoices in a good that is at once shared by all and unchanging—a love that makes ‘one heart’ out of many (Acts 4:32); a love that is the whole-hearted and harmonious obedience of mutual affection. (City of God, 15)
The church is a community constituted by a sharing in Christ through love. What a beautiful thing the church is (at least when seen by faith).