Pope John Paul II
Dominum et Vivificantem §50
Part III - The Spirit Who Gives Life
50 The great Jubilee at the close of the second Millennium, for which the Church is already preparing, has a directly Christological aspect: for it is a celebration of the birth of Jesus Christ. At the same time it has a pneumatological aspect, since the mystery of the Incarnation was accomplished "by the power of the Holy Spirit." It was "brought about" by that Spirit-consubstantial with the Father and the Son-who, in the absolute mystery of the Triune God, is the Person-love, the uncreated gift, who is the eternal source of every gift that comes from God in the order of creation, the direct principle and, in a certain sense, the subject of God's self- communication in the order of grace. The mystery of the Incarnation constitutes the climax of this giving, this divine self-communication. The conception and birth of Jesus Christ are in fact the greatest work accomplished by the Holy Spirit in the history of creation and salvation: the supreme grace "the grace of union," source of every other grace, as St. Thomas explains. The great Jubilee refer to this work and also-if we penetrate its depths-to the author of this work, to the person of the Holy Spirit. For the "fullness of time" is matched by a particular fullness of the self- communication of the Triune God in the Holy Spirit. "By the power of the Holy Spirit" the mystery of the "hypostatic union" is brought about-that is, the union of the divine nature and the human nature, of the divinity and the humanity in the one Person of the Word-Son. When at the moment of the Annunciation Mary utters her "fiat": "Be it done unto me according to your word," she conceives in a virginal way a man, the Son of Man, who is the Son of God. By means of this "humanization" of the Word-Son the self-communication of God reaches its definitive fullness in the history of creation and salvation. This fullness acquires a special wealth and expressiveness in the text of John's Gospel: ''The Word became flesh." The Incarnation of God the Son signifies the taking up into unity with God not only of human nature, but in this human nature, in a sense, of everything that is "flesh": the whole of humanity, the entire visible and material world. The Incarnation, then, also has a cosmic significance, a cosmic dimension. The "first-born of all creation," becoming incarnate in the individual humanity of Christ, unites himself in some way with the entire reality of man, which is also "flesh" -and in this reality with all "flesh," with the whole of creation.
Source: Dominum et Vivificantem (Vatican.va)