Catechism of the Catholic Church §854 — excerpt
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."
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: GS 40 # 2 · RMiss 42 47 · AG 15 # 1 · RMiss 48-49 · RMiss 52-54 · AG 6 # 2