That they may be one, even as we are one, Christ cries out to his Father; (John 17:11) that they may all be one; even as thou, Father, art in me and I in thee; that they also may be in us. (John 17:21) This exhortation to unity flows in a constant stream from the lips of Jesus, for every kingdom divided against itself is laid waste, and no city or house divided against itself will stand. (Matthew 12:25) It is a teaching which is converted into a vehement desire: And I have other sheep that are not of this fold; I must bring them also, and they will heed my voice. So there shall be one flock, one shepherd. (John 10:16)

What beautiful tones Our Lord uses to express this doctrine! He multiplies words and images so that we may understand it, so that this passion for unity may remain engraved on our souls. I am the true vine and my Father is the vinedresser. Every branch of mine that bears no fruit, he takes away, and every branch that does bear fruit he prunes that it may bear more fruit... Abide in me, and I in you. As the branch cannot bear fruit by itself unless it abides in the vine, neither can you, unless you abide in me. I am the vine, you are the branches. He who abides in me, and I in him, he it is that bears much fruit, for apart from me you can do nothing. (John 15:1-5)

Do you not see how those who separate themselves from the Church, even though they are full of foliage, quickly dry up, and their very fruits are converted into a living bed of worms? Love the holy, roman, apostolic Church. One! For as Saint Cyprian writes: He who reaps elsewhere, outside the Church, dissipates the Church of Christ. And Saint John Chrysostom insists: Do not separate yourself from the Church Nothing is stronger than the Church. Your hope is the Church; your salvation is the Church; your refuge is the Church. It is higher than the heavens, and broader than the earth; it never grows old, its vigour is eternal.

To defend the unity of the Church is to live very united to Jesus Christ who is our vine. How? By growing in fidelity to the perennial Magisterium of the Church: For the Holy Spirit was promised to the successors of Peter not that they should manifest a new doctrine by his revelation, but rather that with his assistance, they should religiously safeguard and faithfully teach the revelation that was handed down through the Apostles — the deposit of faith. (Vatican I, Dogmatic Constitution on the Church) By venerating this Mother of ours without stain, and loving the Roman Pontiff, we will preserve unity. (In Love With The Church, 3)

Faithfulness to the Pope includes a clear and definite duty: that of knowing his thought, which he tells us in Encyclicals or other documents. We have to do our part to help all Catholics pay attention to the teaching of the Holy Father, and bring their everyday behaviour into line with it. (The Forge, 633)

Offer your prayer, your atonement, and your action for this end: ut sint unum! — that all of us Christians may share one will, one heart, one spirit. This is so that omnes cum Petro ad Iesum per Mariam — that we may all go to Jesus, closely united to the Pope, through Mary. (The Forge, 647)