From Pope Benedict’s Pentecost homily (translation on Zenit):
….We find the elements of wind and fire again at the Pentecost of the New Testament but without the resonances of fear. In particular the fire takes the form of tongues that come to rest upon all the disciples, “who were all full of the Holy Spirit” and on account of that outpouring, “began to speak in other languages” (Acts 2:4). We have here the community’s true “baptism” with fire, a kind of new creation. At Pentecost the Church is not constituted by a human will, but by the power of the Spirit of God. And it immediately appears how this Spirit gives life to a community that is at the same time one and universal, thus overcoming the curse of Babel (cf. John 11:7-9). Only the Spirit, in fact, which creates unity in love and in the reciprocal acceptance of diversity, can liberate humanity from the constant tension of an earthly will-to-power that wants to dominate and make everything uniform.
“Societas Spiritus,” society of the Spirit: This is what St. Augustine calls the Church in one of his sermons (71, 19, 32: PL 38, 462). But already before him, St. Irenaeus formulated a truth that I would like to recall here: “Where the Church is, there is the Spirit of God, and where the Spirit of God is, there is the Church and every grace, and the Spirit is truth; to distance yourself from the Church is to reject the Spirit” and thus “to exclude yourself from life” (Adv. Haer. III, 24, 1). Beginning with the event of Pentecost, this connubium or “marriage” is manifested between the Spirit of Christ and his mystical body, that is, the Church.
I would like to reflect on a particular aspect of the Holy Spirit, on the intertwining of multiplicity and unity. The second reading speaks about this, treating of the harmony of the different charisms in the communion of the same Spirit. But already in the passage from Acts that we have listened to, this intertwining reveals itself with extraordinary evidence. In the event of Pentecost it is made clear that multiple languages and different cultures belong to the Church; they can understand and make each other fruitful. St. Luke clearly wants to convey a fundamental idea, namely, in the act itself of her birth the Church is already “catholic,” universal. She speaks all languages from the very beginning, because the Gospel that is entrusted to her is destined for all peoples, according to the will and the mandate of the risen Christ (cf. Matthew 28:19). The Church that is born at Pentecost is not above all a particular community — the Church of Jerusalem — but the universal Church, that speaks the language of all peoples. From her, other communities in every corner of the world will be born, particular Churches that are all and always actualizations of the one and only Church of Christ. The Catholic Church is therefore not a federation of churches, but a single reality: The universal Church has ontological priority. A community that is not catholic in this sense would not even be a Church.
In this regard it is necessary to add another aspect: that of the theological vision of the Acts of the Apostles in respect of the journey of the Church from Jerusalem to Rome. Luke notes that among the peoples represented in Jerusalem on the day of Pentecost there are also “foreigners from Rome” (Acts 2:10). At that time Rome was still distant, “foreign” for the nascent Church: It was a symbol of the pagan world in general. But the power of the Holy Spirit will guide the steps of the witnesses “to the ends of the earth” (Acts 1:8), to Rome. The Acts of the Apostles ends precisely when Paul, by providential design, arrives at the empire’s capital and proclaims the Gospel there (cf. Acts 28:30-31). Thus the journey of God’s Word, begun in Jerusalem, arrives at its goal, because Rome represents the whole world and thus incarnates the Lucan idea of catholicity. The universal Church is realized, the catholic Church, which is the continuation of the chosen people and makes its history and mission her own….