34 Thanks to ecumenical dialogue we can speak of a greater maturity in our common prayer for one another. This is possible inasmuch as dialogue also serves as an examination of conscience . In this context, how can we fail to recall the words of the First Letter of John? "If we say we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, God is faithful and just, and will forgive our sins and cleanse us from all unrighteousness" (1:8-9). John even goes so far as to state: "If we say that we have not sinned, we make him a liar, and his word is not in us" (1:10). Such a radical exhortation to acknowledge our condition as sinners ought also to mark the spirit which we bring to ecumenical dialogue. If such dialogue does not become an examination of conscience, a kind of "dialogue of consciences", can we count on the assurance which the First Letter of John gives us? "My little children, I am writing this to you so that you may not sin; but if any one does sin, we have an advocate with the Father, Jesus Christ the righteous ; and he is the expiation for our sins, and not for ours only but also for the sins of the whole world" (2:1-2). All the sins of the world were gathered up in the saving sacrifice of Christ, including the sins committed against the Church's unity: the sins of Christians, those of the pastors no less than those of the lay faithful. Even after the many sins which have contributed to our historical divisions, Christian unity is possible , provided that we are humbly conscious of having sinned against unity and are convinced of our need for conversion. Not only personal sins must be forgiven and left behind, but also social sins, which is to say the sinful "structures" themselves which have contributed and can still contribute to division and to the reinforcing of division.
Source: Ut Unum Sint (Vatican.va)