The Eastern and the Western churches were happily united until the fourth and fifth centuries, when the heresiarchs Arius, Nestorius and Eutyches withdrew millions of souls from the centre of unity. The followers of these sects were called, after their founders, Arians, Nestorians and Eutychians, and from that day to the present the two latter bodies have formed distinct communions, being separated from the Catholic Church in the East, just as the Protestant churches are separated from her in the West.
The Greek schismatic church, of which the present Russo-Greek church is the offspring, severed her connection with the See of Rome in the ninth century.
But in leaving the Catholic Church these Eastern sects retained the old Liturgies, which they use to this day, as I shall presently demonstrate.
During my sojourn in Rome at the Ecumenical Council I devoted a great deal of my leisure time to the examination of the various Liturgies of the schismatic churches of the East. I found in all of them formulas of prayers for the dead almost identical with that of the Roman Missal: "Remember, O Lord, Thy servants who are gone before us with the sign of faith, and sleep in peace. To these, O Lord, and to all who rest in Christ grant, we beseech Thee, a place of refreshment, light and peace, through the same Jesus Christ our Lord."
Not content with studying their books, I called upon the Oriental Patriarchs and Bishops in communion with the See of Rome, who belong to the Armenian, the Chaldean, the Coptic, the Maronite and Syriac rites. They all assured me that the schismatic Christians of the East among whom they live have, without exception, prayers and sacrifices for the dead.
Now, I ask, when could those Eastern sects have commenced to adopt the Catholic practice of praying for the dead? They could not have received it from us since the ninth century, because the Greek church separated from us then and has had no communion with us since that time, except at intervals, up to the twelfth century. Nor could they have adopted the practice since the fourth or fifth century, inasmuch as the Arians, Nestorians and Eutychians have had no religious communication with us since that period. Therefore, in common with us, they received this doctrine from the Apostles. If men living in different countries drink wine having the same flavor and taste and color, the inference is that the wine was made from the same species of grape. So must we conclude that this refreshing doctrine of intercession for the dead has its root in the Apostolic tree of knowledge planted by our Savior.