CATECHISM OF THE CATHOLIC CHURCH
SECOND EDITION

Paragraphs 854–857

854 By her very mission, "the Church . . . travels the same journey as all humanity and shares the same earthly lot with the world: she is to be a leaven and, as it were, the soul of human society in its renewal by Christ and transformation into the family of God." Missionary endeavor requires patience. It begins with the proclamation of the Gospel to peoples and groups who do not yet believe in Christ, continues with the establishment of Christian communities that are "a sign of God's presence in the world," and leads to the foundation of local churches. It must involve a process of inculturation if the Gospel is to take flesh in each people's culture. There will be times of defeat. "With regard to individuals, groups, and peoples it is only by degrees that [the Church] touches and penetrates them and so receives them into a fullness which is Catholic."
855 The Church's mission stimulates efforts towards Christian unity. Indeed, "divisions among Christians prevent the Church from realizing in practice the fullness of catholicity proper to her in those of her sons who, though joined to her by Baptism, are yet separated from full communion with her. Furthermore, the Church herself finds it more difficult to express in actual life her full catholicity in all its aspects."
856 The missionary task implies a respectful dialogue with those who do not yet accept the Gospel. Believers can profit from this dialogue by learning to appreciate better "those elements of truth and grace which are found among peoples, and which are, as it were, a secret presence of God." They proclaim the Good News to those who do not know it, in order to consolidate, complete, and raise up the truth and the goodness that God has distributed among men and nations, and to purify them from error and evil "for the glory of God, the confusion of the demon, and the happiness of man."
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," the witnesses chosen and sent on mission by Christ himself;

- with the help of the Spirit dwelling in her, the Church keeps and hands on the teaching, the "good deposit," the salutary words she has heard from the apostles;

- 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":

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. . . .