Personhood and being -- From mask to person : the birth of an ontology of personhood -- From biological to ecclesial existence : the ecclesiological significance of the person -- Truth and communion -- Introduction : the problem of truth in the Patristic Era -- Truth, being and history : the Greek Patristic synthesis -- Truth and salvation : the existential implications of truth as communion -- Truth and the church : ecclesiological consequences of the Greek Patristic synthesis -- Christ, the Spirit and the Church -- The problem of the synthesis between Christology and Pneumatology -- Implications of the synthesis for ecclesiology -- Eucharist and Catholicity -- The "one" and the "many" in the Eucharistic consciousness of the early church -- The composition and structure of the Eucharistic community as reflections of Catholicity -- The Eucharistic community and the "Catholic church in the world" -- Apostolic continuity and succession -- The two approaches, "historical" and "eschatological," to apostolic continunity -- Towards a synthesis of the "historical" and the eschatological" approach -- Concrete consequences for the life of the church -- Conclusion for the ecumenical debate -- Ministry and communion -- The theological perspective -- The relational character of ministry -- The "sacramental" character of the ministry -- Ministry and unity -- The "validity" of the ministry -- The local church in a perspective of communion -- The historical and ecclesiological background -- Questions concerning the theology of the local church today.