Hebrew Scriptures and New Testament
Trinity and entire conciliar understanding of the nature of God (minus the Filioque). This always gets underrated, but SERIOUSLY, we agree on who God is, this is a big deal.
Prayer (for the most part, minus Protestants on saintly intercession)
Ethics (conservatives in each group all hold biblical values on most ethical issues, liberals are another matter)
Love and Social Justice
Justification by Grace
Metaphysics (I don't think Protestants or Orthodox disagree with Catholics here, but I might be wrong).
The Apostles and Nicene Creed (except for non-Lutheran Protestants objecting to "one baptism for the forgiveness of sins")
This really is alot if you think about it.
Right after discussing how divided Christendom is over prayers to the saints C.S. Lewis writes:
"I sometimes have a briht dream of reunion engulfing us unawares, like a great wave from behind our backs, perhaps at the very moment when our official representatives are still pronouncing it impossible. Discussions usually separate us; actions sometimes unite us." - C.S. Lewis "Letters to Malcolm: Chiefly on Prayer" Ch.3
I love this image. C.S. Lewis was such a genius. I think there are 3 kinds of Christians out there in terms of ecumenism:
1. Triumphalists. These are the people who actually enjoy the divisions of the church. They like to go on and on about how they are the only remnant left and how God is unknown to everyone else. I think they remind me of Mark Twain's joke about putting a Roman Catholic, a Presbyterian, and a Baptist in a cage and them all killing each other. Indeed those 3 seem to compete for the title of least ecumenical.
2. Compromisers. These are people who want to gloss over every difference imaginable, if they can't outright ignore it. These are the opposite to the triumphalists. But at least the compromisers do something together, whether it's social justice stuff or charity work, they do something. Along with those who know the differences and ignore them, here I'll include those who are simply ignorant of theological divisions.
3. Segregationists. These are people who understand the differences between the different churches/denominations and know why they are _______ists or ________ans but they anxiously await and seek reunion. They believe we are segregated on earth here and now because of our honest disagreement, but that God's grace and the Holy Spirit work universally and that while they may say "outside the church there is ordinarily no salvation" (WCF) but at the same time admit that ordinarily is the key word.
I hope I'm in group 3 and that if I've chosen the "wrong" church after all that He'll be gracious and merciful.
I was watching this movie "The Lilies of the Field" today with Sidney Poitier and it's about a Baptist construction worker / general labourer guy who helps a group of Nuns build a chapel. There's a beautiful scene where he rebukes the Mother Superior and asks if they ever have any joy amidst their "religion" (bad connotation in this usage). It ends with them all singing the Negro Spiritual "Amen" together and smiling as Sidney Poitier is 'lining' the life of Jesus while they sing Amen. Even though it was just a movie, it gave me hope that maybe one day God will teach us to have the Joy of black Baptists and the holiness of German Nuns in perfect harmony.
Lord help us.