"The Church, in Christ, is in the nature of sacrament - a sign and instrument, that is, of communion with God and of unity among all men" (LG, n. 1). This sacramentality must explained in the context of mystery ("mysterium") as it is understood in the first chapter of the Constitution.

The Church is a divine mystery because the divine design (or plan) for humanity's salvation is realized in her, i.e., "the mystery of the kingdom of God" revealed in the word and very life of Christ.

This mystery was revealed by Jesus first of all to the Apostles, "The mystery of the kingdom of God has been granted to you. But to those outside everything comes in parables" (Mk 4,11).

The meaning of the parables of the kingdom is first realized in a fundamental way through the incarnation and finds its fulfillment in the period between the Passover of Christ's cross and resurrection and Pentecost in Jerusalem, where the Apostles and the members of the first community received the baptism of the Spirit of truth.

At the same time the eternal mystery of the divine plan for the salvation of humanity was given its visible form as the Church, the new People of God.

Paul proclaims Christ "according to the revelation of the mystery kept secret for long ages but now manifested" (Rom 16,25-26), "to his holy ones, to whom God chose to make known the riches of the glory of this mystery among the Gentiles; it is Christ in you, the hope for glory" (Col 1,26-27).

This divine mystery is intended "for human beings": " that the Gentiles are co-heirs, members of the same body, and copartners in the promise in Christ Jesus through the Gospel" (Eph 3,5-7).

The eternal initiative of the Father, who conceives the saving plan which was revealed to humanity and accomplished in Christ, is the foundation of the Church's mystery. In the Church, through the work of the Holy Spirit, the mystery is shared with human beings, beginning with the Apostles.

In the Latin Church the word sacramentum has acquired the more specific meaning of designating the seven sacraments. Applying this meaning to the Church can be done only in an analogous way.

According to the teaching of the Council of Trent, a sacrament "is a sign of a sacred reality and the visible expression of invisible grace" and this can only refer to the Church in an analogical sense.

The Church is a sign, but not only a sign; in herself she is also the fruit of redemption. The sacraments are means of sanctification; the Church, in-stead, is the assembly of the persons sanctified; thus, she constitutes the purpose of the saving action (cf. Eph 5,25-27).

The Church is indeed the sign of the salvation accomplished by Christ and meant for all human beings through the work of the Holy Spirit. The sign is visible, the Church, as the community of God's People, has a visible character. The sign is also efficacious, in as much as belonging to the Church obtains for men union with Christ and all the graces necessary for salvation.

It is not a matter of a substantial identity. One cannot, in fact, attribute the divine institution and effectiveness of the seven sacraments to the whole of the Church's functions and ministries. Moreover, there is a substantial presence of Christ in the Eucharist, and certainly that cannot be extended to the whole Church.

The organic connection between the Church as Sacrament and the individual sacraments is especially close and essential in regard to the Eucharist, Actually, inasmuch as the Church (as sacrament) celebrates the Eucharist, the Eucharist realizes the Church and makes her present.