The Church, a people gathered into the unity of the Father, the Son and the Holy Spirit, was instituted by our Lord Jesus Christ, as “a sacrament – a sign and instrument, that is, of communion with God and of unity among all people.” Every division among the baptized in Jesus Christ wounds that which the Church is and that for which the Church exists; in fact, “such division openly contradicts the will of Christ, scandalizes the world, and damages that most holy cause, the preaching the Gospel to every creature.” Precisely for this reason, before shedding his blood for the salvation of the world, the Lord Jesus prayed to the Father for the unity of his disciples.
It is the Holy Spirit, the principle of unity, which establishes the Church as a communion. He is the principle of the unity of the faithful in the teaching of the Apostles, in the breaking of the bread and in prayer. The Church, however, analogous to the mystery of the Incarnate Word, is not only an invisible spiritual communion, but is also visible; in fact, “the society structured with hierarchical organs and the Mystical Body of Christ, the visible society and the spiritual community, the earthly Church and the Church endowed with heavenly riches, are not to be thought of as two realities. On the contrary, they form one complex reality formed from a two-fold element, human and divine.”