Here is an interesting moment in modern ecumenism. Pope Francis was recently visited in Rome by the 118th Coptic Pope of Alexandria and Patriarch of the See of St. Mark, Tawadros II. There's about 15,000,000 Coptic Christians, approximately 12,000,000 of them in Egypt, their traditional home.
Pope Francis...prayed for “full unity” with the Coptic Orthodox Church as he received Patriarch of Alexandria Tawadros II for an historic visit in the latest sign of closer ties between the Catholic and Orthodox (sic) worlds.
“We long for the day when, in fulfilment of the Lord’s desire, we will be able to communicate from the one chalice,” he said, acknowledging that there had been “centuries of mutual distrust” between their two Christian churches.
This was the first such meeting in 40 years.
To understand the division between the Coptic Church and Roman Catholicism, one has to look to the split between the Oriental Orthodox churches--of which the Coptic Church is one--and the dominant churches of the West and East, which occured as a result of the Council of Chalcedon in A.D. 451, the Fourth Ecumenical Council, due to what the modern mind almost certainly sees as a technicality.