Oecumene volgens paus Leo XIII

"But how can hearts be united in perfect Charity where minds do not agree in Faith?"

Uit de encycliek Præclara Gratulationis Publicæ (1894)
"The Principal subject of contention is the Primacy of the Roman Pontiff. But let them look back to the early years of their existence, let them consider the sentiments entertained by their forefathers, and examine what the oldest Traditions testify, and it will, indeed, become evident to them that Christ's Divine Utterance, Thou art Peter, and upon this rock I will build My Church, has undoubtedly been realized in the Roman Pontiffs. Many of these latter in the first gates of the Church were chosen from the East, and foremost among them Anacletus, Evaristus, Anicetus, Eleutherius, Zosimus, and Agatho; and of these a great number, after Governing the Church in Wisdom and Sanctity, Consecrated their Ministry with the shedding of their blood. The time, the reasons, the promoters of the unfortunate division, are well known. Before the day when man separated what God had joined together, the name of the Apostolic See was held in Reverence by all the nations of the Christian world: and the East, like the West, agreed without hesitation in its obedience to the Pontiff of Rome, as the Legitimate Successor of St. Peter, and, therefore, the Vicar of Christ here on earth. "

"Nor is there any reason for you to fear on that account that We or any of Our Successors will ever diminish your rights, the privileges of your Patriarchs, or the established Ritual of any one of your Churches. It has been and always will be the intent and Tradition of the Apostolic See, to make a large allowance, in all that is right and good, for the primitive Traditions and special customs of every nation. On the contrary, if you re-establish Union with Us, you will see how, by God's bounty, the glory and dignity of your Churches will be remarkably increased."

"It is on this account that many of those We allude to men of sound judgment and seeking after Truth, have looked to the Catholic Church for the sure way of salvation; for they clearly understand that they could never be united to Jesus Christ, as their Head if they were not members of His Body, which is the Church; nor really acquire the True Christian Faith if they rejected the Legitimate teaching confided to Peter and his Successors"