The Catholic Church is a mystery in history. She is also probably the most misunderstood institution in the world, for many people examine only her history and neglect her mystery. On November 21, 1964, the Vatican II Fathers promulgated Lumen Gentium or the Dogmatic Constitution on the Church to present the truth of the Catholic Church, in all her splendor and complexity, to the modern world. Because this document is so long and so rich, I will summarize it in three parts.
Here's a sampling of the ideas and topics you'll find in the first three chapters of Lumen Gentium.
Chapter I: The Mystery of the Church
* The Church is a sacrament, a sign and instrument of unity with God and among men. The light of Christ shines visibly through the Church.
* God prepared for the Church in the Old Testament when He called the people of Israel to be His own. The Church was established by Jesus and made manifest in the Holy Spirit. She will reach her fulfillment at the end of time.
* The Church is the family of God and the Kingdom of Heaven “already present in mystery.” She originated from the blood and water that flowed from the side of Jesus as He hung dead on the cross.
* At Pentecost the Holy Spirit was poured out upon the infant Church. The Spirit sanctifies the Church so that her members may have access to God. The Spirit indwells the Church to guide her, unify her, bestow gifts upon her, direct her, and adorn her with His fruits. The Spirit, as the soul of the Church, leads the Church into the perfect unity with God that springs from the unity of the Trinity.
* Jesus founded the Church in His words, in His works, and in His very Person. The Church's mission is to proclaim the Kingdom of God to all people and establish the Kingdom throughout the world.
* There are numerous images and symbols of the Church that help make her known. These include a sheepfold, the gate to which is Christ; a cultivated field; the building of God; the temple; the new Jerusalem; our mother; the spotless bride of Christ; a pilgrim; and the Body of Christ.
* The Church communicates the life of Christ to those who have faith and are united to Christ through the sacraments. The members of the Church are also intimately united with each other.
* The Church is a body with “a diversity of members and functions” but only one Spirit, Who gives the Body unity.
* Christ is the Head of the body, which He forms in His likeness. The Church shares in Christ's suffering that she may be gloried with Him. Christ fills the Church, His bride, with divine gifts that she may attain fullness.
* The Church is both visible and invisible, human and divine, in imitation of the Incarnate Word of God. The visible, earthly structure of the Church serves her invisible, heavenly nature.
* The Catholic Church is one, holy, catholic, and apostolic, and the Church that Jesus founded subsists, or stands firm, in the Catholic Church, which is led by the pope and bishops, who are successors of Peter and the apostles.
* The Church experiences poverty, oppression, and trials in union with Christ. She reaches out with love to those who suffer. Because her members are sinners, she always walks “the path of penance and renewal” even those she herself is holy and pure.
Chapter II: The People of God
* God made a people for Himself. In the old covenant, that people was Israel; in the new covenant, it is the Church, which is made up of baptized believers and is the new People of God.
* The Church is a messianic people. She was established by Christ “as a communion of life, love, and truth.” She is a light to the world and Christ's instrument of salvation. The Church has entered into human history but also transcends all times and boundaries.
* The Holy Spirit continually renews the Church. She relies on God's grace in all her trials.
* The baptized share in the priesthood of Christ. They offer themselves and their spiritual sacrifices to God and bear witness to Christ.
* The sacraments strengthen the faithful, immerse them in God's grace, and help them on their path to sanctity.
* The people of God also share in the prophetic office of Christ, as they witness to Him by their lives of faith and love. Through the sensus fidei, the entire body of the faithful manifests “a universal consent in matters of faith and morals” under the guidance of the Spirit. The faithful are obliged to hear and obey the Word of God given through Sacred Scripture and Sacred Tradition and interpreted by the Magisterium.
* The Blessed Trinity is the source of all the gifts given to the Church and her members. These gifts must be used to renew and build up the Church.
* All people are called to belong to the Church, which is unified by the Holy Spirit.
* The Church is universal. Her members exist in unity even in their diversity of roles and duties. The faithful share in a community of “spiritual riches, apostolic workers and temporal resources,” and they must be good stewards of God's grace that with their common effort they may grow in holiness and contribute to the good of the whole Church.
* The Church is necessary for salvation.
* Those who are fully incorporated into the Catholic Church are joined to the Church's visible structure and share a common faith, the sacraments, and ecclesiastical governance. These “children of the Church” must remember that they live in an “exalted condition” in the fullness of the faith by the grace of God.
* Other Christians who are baptized but not in full communion with the Catholic Church are still joined to the Church in many ways. Elements of salvation may be found outside of the visible confines of the Church, but these elements are ordered to unity and designed to draw people into full communion with the Catholic Church.
* God wills that all people be saved, and His mercy works in mysterious ways to draw people to Himself.
* The Church is obliged to spread the Gospel everywhere and cooperate in God's plan to save the whole world.
Chapter III: The Church is Hierarchical
* Jesus Christ founded the Church and established a hierarchy to shepherd His people and guide them to salvation.
* The pope is the successor of Peter, and the bishops are successors of the apostles. The pope is the “lasting and visible source and foundation of the unity both of faith and of community.”
* The pope and bishops act in the Person and power of Christ to preach the Gospel, govern the Church, and sanctify and guide the faithful. The apostolic succession and divine mission of the hierarchy will last until the end of time that the Gospel may spread throughout the world.
* The bishops receive the fullness of the sacrament of Holy Orders. United with each other, they form a “unique apostolic college” with the pope as their head.
* As the Vicar of Christ, the pope serves as “pastor of the entire Church” and holds “full, supreme and universal power” over the Church. He is the “visible source and foundation of unity” for the bishops and the faithful, and guided by the Holy Spirit, he speaks infallibly when he “proclaims in an absolute decision a doctrine pertaining to faith or morals.”
* The body of bishops, especially when they are gathered into an ecumenical council under the leadership of the pope, may also speak infallibly about faith and morals.
* The faithful must submit to the pope and bishops in “matters of faith and morals” and obey them with “a ready and respectful allegiance of mind.”
* Bishops must care for the faithful entrusted to them with great love as they teach, govern, and sanctify.
* Priests cooperate with the bishops in preaching the Gospel, shepherding the faithful, and celebrating divine worship. Priests work to build up the Body of Christ and bear witness to the truth in love.
* Deacons serve the faithful and assist the bishops and priests by “works of charity and functions of administration.”
The full text of Lumen Gentium is available online at the Vatican website.