I found this an interesting comment in a paper I am editing.
Miroslav Volf has talked about “openness of every church toward all other churches as an indispensable condition of ecclesiality”. He says: “Since the eschatological gathering of the people of God, whose foretaste is the local church, is not identical with all churches of the past and present, the ecclesiality of a local church need not depend on the sacramental relation to them. Yet since the eschatological gathering of the people of God will include all these churches as its own anticipations, a local church cannot alone, in isolation from all other churches, claim to be a church. It must acknowledge all others churches, in time and space, as churches, and must at least be open to diachronic and synchronic communication with them.”
Title of paper: The Commemoration of the Reformation as an Ecumenical Opportunity: A Free Church Perspective