First, what does ecumenism mean? It does not mean that we should accept all our differences as minor details that are not important. It means that we focus on our common beliefs and join in respectful dialogue to fully understand our differences. The goal of this dialogue is primarily to affirm our common faith, but also to convert the other party in the dialogue. The attempt to convert should not be a forceful attack on the other's faith, nor should it be a one-sided "exchange" of ideas. It should be a mutual exchange of ideas where each party it trying his best to understand the other point of view. (I've failed badly at not being forceful. I pray that I start doing this tomorrow. And, tomorrow I'll probably make the same prayer...) If my faith seems more reasonable to you, you will convert to my faith. If your faith seems more reasonable to me, I will convert to your faith. If a person is not comfortable with such dialogue, he is not confident in his faith. (I am so confident in my faith that there is no issue that I am uncomfortable discussing; even the issues I don't understand. I've given up second guessing Holy Mother Church years ago.)
Even when no conversion happens, we can work together towards common goals in society. This was clearly demonstrated a few years ago with Proposition 8 in California. Catholics and Mormons worked hand in hand to get this passed, not to mention the Orthodox, Jews and Evangelical Christians. When we focus on our common beliefs, we can make a difference in society. Many times the Holy See allies itself with Islamic states in the United Nations to do this. Ecumenical dialogue and interfaith dialogue are very similar and have almost the same goal. The only difference is that ecumenical dialogue hopes to bring a united Christian Faith to interfaith dialogue.
With such open dialogue, no one should be offended at being called a heretic or an apostate. These are technical terms and all the baggage they carry should be discarded. If I didn't think the other person in the dialogue was a heretic, then I wouldn't have confidence that I am not a heretic, and vice versa. I expect other Christians to think that I am a heretic. In so doing, it shows that they also think that I am a Christian, as the word heretic implies. I even understand when some Christians think that I am an apostate as I also believe that there are some Christian-like churches that have so distorted the Christian Faith that they are no longer Christian, such as Mormons and Jehovah's Witnesses (note that I praised Mormons earlier for working hand in hand with Catholics). The terms heretic and apostate should not be used in a derogatory manner, but express how other faiths relate to your own.
From almost the beginning, there has been two ways to be Christian: orthodox and heretical. Presently, there are more than 28,000 ways to be a heretical Christian and counting. For a heretical Christian to become an orthodox Christian usually involves the process known as R.C.I.A., or Rite of Christian Initiation of Adults. This process was originally intended to bring non-Christians into the Church, but it has been adapted to also bring heretics into full communion with the Church (I was one of them). Most heretic baptisms are valid, so full initiation culminates in the Sacrament of Conformation and First Eucharist. Technically, if one's baptism isn't valid or if one has not been baptized, it's questionable if that person can be called a Christian; although, baptism of desire may qualify. In such cases, these persons receive the Sacrament of Baptism before Conformation and Eucharist. If the validity of a heretic baptism is questionable, conditional baptism is applied where God knows which baptism was the valid one.
One "heretical" church that is not quite like the other 28,000 is part of the Anglican Church. There are a number of loosely connected churches within the Anglican Church, some of which the term heretic doesn't quite fit. Their Sacrament of Holy Orders is invalid not because of heresy, but because of a technical detail found throughout a particular century of their history. Thus, the only sacrament of initiation of theirs that is valid is Baptism. However, there isn't anything really doctrinal that separates them from the orthodox Faith, so R.C.I.A. isn't really applicable. Hence, we now have the Anglican Ordinariate.
There are primarily two ways to be an orthodox Christian: Western and Eastern. To be a Western orthodox Christian, one would almost always be a Roman Catholic. There are a couple other Latin Rites, but they are extremely small. I actually know next to nothing about them other than that they exist. For the sake of brevity, when I refer to the Roman Church, I include the other Latin Rites.
To be an Eastern orthodox Christian, one can belong to one of three different groupings of churches: the Eastern Catholic Churches, the Eastern Orthodox Churches and the Oriental Orthodox Churches. It is within these three groupings of churches that I see the hope of full communion without any need for conversion as there is with the heretical churches. In essence, these churches share full doctrinal unity with the Roman Catholic Church; although, we must look very hard to see this unity. The problem is that many, both from the East and the West, refuse to look for this unity.
The Oriental Orthodox Churches became separated from the rest of orthodox Christianity after refusing to accept the terminology of the Council of Chalcedon in the 5th century. The rest of Christendom labeled them as Monophysite heretics; however, this was an incorrect label. The rejection of the Council of Chalcedon by the Oriental Orthodox Churches was not due to doctrinal differences over the nature of Christ, but in expressing the understanding of the nature of Christ. For the Oriental Orthodox, to say that Christ has a Divine Nature and a Human Nature is to divide Christ. However, they agree that the dynamic permanence of Christ's Divinity and Christ's Humanity, with their proper energies and wills, without confusion and without change, are united hypostatically in the Person of Christ. The language is different, but the essences is the same. Thus, it is evident that nothing separates us in Faith.
While it may be difficult for some to fully comprehend how the Oriental Orthodox Churches is doctrinally united with the rest of orthodox Christianity, and it will take a great deal of dialogue to work this out, there is even less difficulty in seeing the doctrinal unity between the Eastern Orthodox Churches and the Eastern and Western Catholic Churches. If you really think about it, these titles convey an incorrect vision of these churches. There really is only the Eastern Churches and the Western Church, which together make up the catholic orthodox Church.
Although there have been various splits between East and West in the first millennium of Church history, parts of the East at times falling into heresy, it is the split of 1054, which renewed a split that occurred a century earlier that had been healed, that leaves us with the present disunity. This split put the Roman Church and the Maronite Church on one side, and the rest of the Eastern Churches on the other. There are a number of different reasons for this split, and many different interpretations of history around this split. I cannot even begin to expound on the subject within the confines of such and insignificant document as this, and I am woefully unqualified to add to the documents that already exist. I will, however, make a very simplistic analogy of the split for those that do not wish to delve deeper into the subject.
Suppose you have a married couple that have a marriage that no tribunal would annul (excuse my use of the Roman Catholic concept of annulment). Over the years, they spend less time with each other and even less time talking to each other. What little time the man spends talking to the woman is spent making demands that she submit to his authority. What little time the woman spends talking to the man is spent belittling what authority the man actually has, which is one of service to the woman. The actually exchange between them does not directly acknowledge the true underlying issues, but focuses on petty issues that only take the place of meaningful discussion. In the end, they divorce, but, like I already said, there are no grounds for annulment.
Since the divorce of 1054, there have been doctrinal developments in the West that have not occurred in the East. For this reason, some in the West consider those in the East heretics, and, likewise, some in the East consider those in the West heretics. This is unproductive. If anyone in the West call the Eastern Christians heretics because of their lack of these doctrinal developments, they will also have to call St. Thomas Aquinas a heretic. Aquinas is arguably the greatest theologian, and I use that term in the Western academic sense, the Roman Church has ever known, and yet, some of what he believed is contrary to how some doctrines later developed. Likewise, Eastern Christians cannot call Roman Christians heretics over doctrinal developments that occurred in the West because these developments are based on beliefs that exist both in the East and the West.
I will give one example that involves conflict between Aquinas and later developments in addition to conflict between East and West: the Immaculate Conception. Aquinas believed Mary was immaculate, the question he struggled with was: At what point was she immaculate? Likewise, Eastern Christians believe Mary was immaculate, it's even stated in their liturgy; however, unlike the West, they do not raise the question that Aquinas raised, but leave it as a mystery. This question is similar to another question that Aquinas struggled with: At what point does life begin? Of course we all now take the answer for granted: at conception.
The divorce of 1054 was not the final word. There have been attempts at reunion, most notably at the Second Council of Lyon in the 13th century, and even more notably at the Council of Florence in the 15th century. At this later council, all but one of the Eastern bishops accepted the West's use of the Filióque, the understanding of purgatory and papal primacy. This clearly demonstrated that there are no doctrinal differences between East and West. Unfortunately, the Eastern laity did not accept the ruling of their bishops. This, alas, is the biggest hurtle I see before unity will be restored between East and West: the laity have to reconcile their differences.
Parts of the East have reconciled with the West. This is how the Eastern Catholic Churches came into being. They are not really separate churches from the Orthodox Churches, but parts of the Orthodox Churches that have reconciled with Rome. In essence, they are the children caught between their divorced parents that have left their mother's house to live with their father without denying they are still their mother's children. This is why I said earlier that there is really only the Eastern Churches and the Western Church, which together make up the catholic orthodox Church. The Eastern Catholic Churches and the Eastern Orthodox Churches are really the same churches. The only differences is that the Eastern Catholic Churches have reconciled with the West.
These children caught between their divorced parents, I believe, are the key to union. It is their relationship with their father, the Roman Catholic Church, and their relationship with their mother, the Eastern Orthodox Churches, that will reconcile their parents divorce. The biggest hurtle, as I already alluded to, is the other children, that is, the Roman Catholic laity and the Eastern Orthodox laity.
There is a lot of hurt that has to heal. This hurt has a strong memory. I think of Orthodox protesters holding a sign that says, "Remember 1204," during a papal visit. This sign is referring to the Forth Crusade in which Roman Catholics sacked Constantinople, the See of the Greek Orthodox Church; the very people they were supposed to help.
We don't even have to go back that far in history to find major hurt. We can even find it here in North America in a betrayal of the reconciliation on the part of the Roman Catholic Church. When Eastern Catholics began emigrating to America, their priests began to follow along with the priests' wives and children. (In case this is news for you, priestly celibacy is a Roman discipline. Married men in the Eastern Catholic Churches can become priests.) The Roman Catholics, in their ignorance, were scandalized by married Catholic priests, so Rome declared that only celibate Eastern priests could minister in the New World. This unjust ruling practically drove many Eastern Catholic Christians in America into going back to live with their mother, the Orthodox Churches. This unjust ruling wasn't even corrected until recently by Bl. Pope John Paul II.
And this is what ecumenism between East and West must fight: ignorance. Roman Catholics have to realize that they are not the only kids in the house, and the Eastern Orthodox have to acknowledge that Eastern Catholics are really Eastern Orthodox as well. Too many Roman Catholics don't even know that the Eastern Catholic Churches exist, and too many Eastern Orthodox consider Eastern Catholics as some kind of Roman offshoot. There is no doctrine that divides us. We must forgive each other and reconcile our differences.
I'm planning on living for another 40 to 60 years, and it is my hope that before I die, I can receive Communion in an Orthodox Church. I am Roman Catholic, and I will remain Roman Catholic. I privately pray the Nicene Creed every day omitting the Filióque, but I know that such an act is not enough to bring unity. I too have my own baggage; my own interpretation of history. For instance, I cannot at this point acknowledge Photius of Constantinople and Michael Cærularius as St. Photius and St. Cærularius. Honestly, I don't know if I'm right on this issue. I need more dialogue. I need ecumenism.