Rather than quote extracts from the Holy Father's reflection, I suggest that you read it in its entirety.
I recall that, during Pope Benedict's meeting with Christians of other confessions during his visit to Cologne in 2005, the Holy Father drew attention to the unity that already exists among Christians by virtue of their common baptism. If I recall correctly, he asked his listeners not to underestimate the significance of this alreay existing unity. Pope Benedict seems to refer to this at the beginning of his Audience address:
We are celebrating the Week of Prayer for Christian Unity, in which all believers in Christ are invited to join in prayer to witness the profound bond that exists among them and to invoke the gift of full communion....Vatican Council II states "[t]hese prayers in communion are, without a doubt, a very effective means to implore the grace of unity and constitute a genuine manifestation of the bonds with which Catholics remain united with the separated brethren: 'For where two or three are gathered in my name, there am I in the midst of them' (Matthew18:20)" ("Decree Unitatis Redintegratio," No. 8).[Later in his address, when discussing the question of inter-communion, the Holy Father points out that Christians are still "very far" from the fullness of unity willed by Christ for his disciples.]
The Holy Father then unfolds the theme of this years Week of Prayer - "And they devoted themselves to the Apostles' teaching and fellowship, to the breaking of bread and the prayers" (Acts 2:42) - in a representation of four characteristics of the unity of the Church. It is interesting to summarise his development of the theme by comparing it to the last sentence of the Compendium of the Catechism of the Catholic Church n.161:
The Church has but one faith, one sacramental life, one apostolic succession, one common hope and one and the same charity.The care with which Pope Benedict expresses himself is worthy of note. Prayer for unity among Christians is not prayer for the re-unification of the Church - objectively, the Catholic Church considers her unity to have not been lost. Instead, the prayer is one for the achievement of full communion among those who are Christians. The Pope's affirmation that:
...every effort made for the building of unity between Christians passes through the deepening of fidelity to the depositum fidei which the Apostles transmit to us. Firmness in the faith is the basis of our communion, it is the basis of Christian unity.is diplomatic, but interesting, in this context.
Another aspect of Pope Benedict's words that I would like to draw attention to is the discussion of fraternal communion. Within my own experience, there are two areas of pastoral action in which joint action with Christians of other denominations is very much taken for granted. One is hospital visiting, where certainly some NHS hospital trusts have "generic visiting" arrangments (these arrangments are supported by denomination and faith specific referral and chaplaincy arrangements). In my experience, most of the visitors who undertake the regular ward visiting are Christians, though in principle other faiths also participate. The second is ship visiting in ports, where the Apostleship of the Sea works closely with other Christian organisations. In both contexts, the way in which Christians of different denominations work alongside each other means that "more patients are visited" and "more ships are visited" as a result.
Communion with God, made flesh in fraternal communion, is translated, concretely, in social effort, in Christian charity, in justice.This ordinary level of common action between Christians is, in my view, a more genuine expression of ecumenical activity than special services or preaching exchanges.