In the Church there is a diversity of ministry but a oneness of mission. Christ conferred on the Apostles and their successors the duty of teaching, sanctifying, and ruling in His name and power. But the laity likewise share in the priestly, prophetic, and royal office of Christ and therefore have their own share in the mission of the whole people of God in the Church and in the world.
They exercise the apostolate in fact by their activity directed to the evangelization and sanctification of men and to the penetrating and perfecting of the temporal order through the spirit of the Gospel. In this way, their temporal activity openly bears witness to Christ and promotes the salvation of men. Since the laity, in accordance with their state of life, live in the midst of the world and its concerns, they are called by God to exercise their apostolate in the world like leaven, with the ardor of the spirit of Christ.
The laity derive the right and duty to the apostolate from their union with Christ the head; incorporated into Christ’s Mystical Body through Baptism and strengthened by the power of the Holy Spirit through Confirmation, they are assigned to the apostolate by the Lord Himself. They are consecrated for the royal priesthood and the holy people (cf. 1 Peter 2:4-10) not only that they may offer spiritual sacrifices in everything they do but also that they may witness to Christ throughout the world. The sacraments, however, especially the most holy Eucharist, communicate and nourish that charity which is the soul of the entire apostolate.
One engages in the apostolate through the faith, hope, and charity which the Holy Spirit diffuses in the hearts of all members of the Church. Indeed, by the precept of charity, which is the Lord’s greatest commandment, all the faithful are impelled to promote the glory of God through the coming of His kingdom and to obtain eternal life for all men-that they may know the only true God and Him whom He sent, Jesus Christ (cf. John 17:3). On all Christians therefore is laid the preeminent responsibility of working to make the divine message of salvation known and accepted by all men throughout the world. – Address of His Holiness to the Second World Congress of the Lay Apostolate October 5, 1957
