From The Catechism Of The Catholic Church:
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IV. THE CHURCH IS APOSTOLIC
857 The Church is apostolic because she is founded on the apostles, in three ways:
- she was and remains built on "the foundation of the Apostles,"362 the witnesses chosen and sent on mission by Christ himself;363
- with the help of the Spirit dwelling in her, the Church keeps and hands on the teaching,364 the "good deposit," the salutary words she has heard from the apostles;365
- she continues to be taught, sanctified, and guided by the apostles until Christ's return, through their successors in pastoral office: the college of bishops, "assisted by priests, in union with the successor of Peter, the Church's supreme pastor":366
You are the eternal Shepherd
who never leaves his flock untended.
Through the apostles
you watch over us and protect us always.
You made them shepherds of the flock
to share in the work of your Son. . . .367
The Apostles' mission
858 Jesus is the Father's Emissary. From the beginning of his ministry, he "called to him those whom he desired; . . . . And he appointed twelve, whom also he named apostles, to be with him, and to be sent out to preach."368 From then on, they would also be his "emissaries" (Greek apostoloi). In them, Christ continues his own mission: "As the Father has sent me, even so I send you."369 The apostles' ministry is the continuation of his mission; Jesus said to the Twelve: "he who receives you receives me."370
859 Jesus unites them to the mission he received from the Father. As "the Son can do nothing of his own accord," but receives everything from the Father who sent him, so those whom Jesus sends can do nothing apart from him,371 from whom they received both the mandate for their mission and the power to carry it out. Christ's apostles knew that they were called by God as "ministers of a new covenant," "servants of God," "ambassadors for Christ," "servants of Christ and stewards of the mysteries of God."372
860 In the office of the apostles there is one aspect that cannot be transmitted: to be the chosen witnesses of the Lord's Resurrection and so the foundation stones of the Church. But their office also has a permanent aspect. Christ promised to remain with them always. The divine mission entrusted by Jesus to them "will continue to the end of time, since the Gospel they handed on is the lasting source of all life for the Church. Therefore, . . . the apostles took care to appoint successors."373
The bishops - successors of the apostles
861 "In order that the mission entrusted to them might be continued after their death, [the apostles] consigned, by will and testament, as it were, to their immediate collaborators the duty of completing and consolidating the work they had begun, urging them to tend to the whole flock, in which the Holy Spirit had appointed them to shepherd the Church of God. They accordingly designated such men and then made the ruling that likewise on their death other proven men should take over their ministry."374
862 "Just as the office which the Lord confided to Peter alone, as first of the apostles, destined to be transmitted to his successors, is a permanent one, so also endures the office, which the apostles received, of shepherding the Church, a charge destined to be exercised without interruption by the sacred order of bishops."375 Hence the Church teaches that "the bishops have by divine institution taken the place of the apostles as pastors of the Church, in such wise that whoever listens to them is listening to Christ and whoever despises them despises Christ and him who sent Christ."376
The apostolate
863 The whole Church is apostolic, in that she remains, through the successors of St. Peter and the other apostles, in communion of faith and life with her origin: and in that she is "sent out" into the whole world. All members of the Church share in this mission, though in various ways. "The Christian vocation is, of its nature, a vocation to the apostolate as well." Indeed, we call an apostolate "every activity of the Mystical Body" that aims "to spread the Kingdom of Christ over all the earth."377
864 "Christ, sent by the Father, is the source of the Church's whole apostolate"; thus the fruitfulness of apostolate for ordained ministers as well as for lay people clearly depends on their vital union with Christ.378 In keeping with their vocations, the demands of the times and the various gifts of the Holy Spirit, the apostolate assumes the most varied forms. But charity, drawn from the Eucharist above all, is always "as it were, the soul of the whole apostolate."379
865 The Church is ultimately one, holy, catholic, and apostolic in her deepest and ultimate identity, because it is in her that "the Kingdom of heaven," the "Reign of God,"380 already exists and will be fulfilled at the end of time. The kingdom has come in the person of Christ and grows mysteriously in the hearts of those incorporated into him, until its full eschatological manifestation. Then all those he has redeemed and made "holy and blameless before him in love,"381 will be gathered together as the one People of God, the "Bride of the Lamb,"382 "the holy city Jerusalem coming down out of heaven from God, having the glory of God."383 For "the wall of the city had twelve foundations, and on them the twelve names of the twelve apostles of the Lamb."384
references:
362 Eph 2:20; Rev 21:14.
363 Cf. Mt 28:16-20; Acts 1:8; 1 Cor 9:1; 15:7-8; Gal 1:1; etc.
364 Cf. Acts 2:42.
365 Cf. 2 Tim 1:13-14.
366 AG 5.
367 Roman Missal, Preface of the Apostles I.
368 Mk 3:13-14.
369 Jn 20:21; cf. 13:20; 17:18.
370 Mt 10:40; cf. Lk 10:16.
371 Jn 5:19, 30; cf. Jn 15:5.
372 2 Cor 3:6; 6:4; 5:20; 1 Cor 4:1.
373 LG 20; cf. Mt 28:20.
374 LG 20; cf. Acts 20:28; St. Clement of Rome, Ad Cor. 42,44 : PG 1,291-300.
375 LG 20 § 2.
376 LG 20 § 2.
377 AA 2.
378 AA 4; cf. Jn 15:5.
379 AA 3.
380 Rev 19:6.
381 Eph 1:4.
382 Rev 21:9.
383 Rev 21:10-11.
384 Rev 21:14.