So much is clear: the Lord’s Supper is the center of the Church and of its various acts of worship. Here the Church is truly itself, because it is wholly with its Lord; here the Church of Christ is gathered for its most intimate fellowship, as sharers in a meal. In this fellowship they draw strength for their service in the world. Because this meal is a meal of recollection and thanksgiving, the Church is essentially a community which remembers and thanks. And because this meal is a meal of covenant and fellowship, the Church is essentially a community, which loves without ceasing. And because finally this meal is an anticipation of the eschatological meal, the Church is essentially a community which looks to the future with confidence. Essentially, therefore, the Church must be a meal-fellowship, a koinonia or communio, must be a fellowship with Christ and with Christians, or it is not the Church of Christ. In the Lord’s Supper it is stated with incomparable clarity that the Church is the ecclesia, the congregation, the community of God. In the Lord’s Supper in fact the Church is constantly constituted anew. If the Church owes to baptism the fact that it is a Church, and does not have to become a Church through its own pious works, the Church owes to the Lord’s Supper the fact that it remains a Church, despite any falling away and failure. From God’s viewpoint it means that while baptism is the sign of electing and justifying grace, the Lord’s Supper is the sign of sustaining and perfecting grace. From the human viewpoint it means that while baptism is above all the sign of the response of faith and obedience, the Lord’s Supper is the sign of the response of love and hope.
—From The Church by Hans Küng