Based on the perspective that the early centuries adopt, the Church finds its initial form in a “communion” whose profound, invisible link is none other than the Spirit of the Lord, but it is the apostolic group in the act of witness that makes up the visible nucleus. The apostolic witness – words and “semia” – centered entirely on the Risen Lord and associated with his Name takes on the aspect of the experienced physical presence of the One who prior to Easter was listened to or “followed” but whose saving work is proclaimed from this moment on. This apostolic martyria manifested and transfigured by the Spirit represents the “visible manifestation” of a God no longer limited to hanging over history but encompassing it, invading it. On the basis of what is acomplished in the Lord Jesus, there is a passionate invasion of human existence, of the personal destiny of every believer but also of Israel’s fate as such and “of all those who are far away, all those whom the Lord our God will call to himself”.
To enter into “communion” is to have a share in this work of God, so as to belong to the mystery of the eschatological period, that which is to be found in the “future” of the human adventure.
J.M.-R. Tillard, Church of Churches: The Ecclesiology of Communion (Collegeville, MN: Michael Glaizer Books, 1992), 6-7.