1 The ardent charity which renders Us solicitous of Our separated brethren, in nowise permits Us to cease Our efforts to bring back to the embrace of the GoodShepherd those whom manifold error causes to stand aloof from the one Fold ofChrist. Day after day We deplore more deeply the unhappy lot of those who aredeprived of the fullness of the Christian Faith. Wherefore moved by the sense ofthe responsibility which Our most sacred office entails, and by the spirit andgrace of the most loving Saviour of men, Whom We unworthily represent, We areconstantly imploring them to agree at last to restore together with Us thecommunion of the one and the same faith. A momentous work, and of all humanworks the most difficult to be accomplished; one which God's almighty poweralone can effect. But for this very reason We do not lose heart, nor are Wedeterred from Our purpose by the magnitude of the difficulties which cannot beovercome by human power alone. "We preach Christ crucified . . . and theweakness of God is stronger than men" (1 Cor. i. 23-25). In the midst of so many errors and of so many evils with which We are afflicted orthreatened, We continue to point out whence salvation should be sought,exhorting and admonishing all nations to lift up "their eyes to themountains whence help shall come" (Ps. cxx.). For indeed that which Isaiasspoke in prophecy has been fulfilled, and the Church of God stands forth soconspicuously by its Divine origin and authority that it can be distinguished byall beholders: "And in the last days the mountain of the house of the Lordshall be prepared on the top of mountains and shall be exalted above thehills" (Is. ii. 2).
Source: Caritatis Studium (Vatican.va)