When a person confesses that Jesus Christ is Lord, all other Christians must take that confession seriously. Such a confession represents the manifest inworking of the Spirit of God (1 Cor 12:3). And it is a call to receive that person as a brother indeed, and to seek to express with him the oneness for which our Lord prayed (John 17:21-23). This is our ecumenical obligation. Indeed, one measure of our obedience to Christ is the extent to which we reach out and identify ourselves with all those who make up the household of faith, regardless how seriously we may disagree with them on matters of faith and practice.
When we speak about the credibility of the church, we have in mind the trustworthiness, the indubitable integrity of the church as messenger of the Kingdom of God. This credibility is of the utmost importance. It is true that the coming of the Kingdom is not brought about by the church itself. The salvation of men and the redemption of the world is the gracious work of God through his Word and Spirit. It is only the Holy Spirit who can kindle faith in the hearts of men.