Is there a biblical ecumenical movement? That depends upon what ecumenical means. If it means seeking religious unity apart from the teachings of the religions, there is not one iota of support for such an effort in the Bible. The Bible sets forth a God Who has spoken and demands faith. That means that in order for men to approach this biblical God, they must come to submission to His teachings (why else has He spoken?). However, if by ecumenical we simply mean seeking unity on the basis of certain core truths, then the Bible obviously pushes very hard in its teachings for such an effort.
Some do not like the idea of certain core truths, but it is inescapable that if we are to have any unity with anyone it cannot be on the basis of common doctrine across the whole range of doctrine. There are no two people in the whole world that believe exactly the same thing about everything. In fact, there is no one person on the planet at the present time who believes everything that God has said. So the quest for unity must be based upon the inescapable core.
And what is that core? That depends upon what realm of unity one is seeking to achieve. If a man and a woman are planning to get married and put themselves under oath to each other and God that they will make their marriage work until one or the other dies, the core is quite large because the unity they seek includes 24 hours of every day. On the other hand, if a group of people are seeking to establish a local church, the core of doctrines which must be agreed upon in advance is not as large as the couple planning marriage, but it must be large enough to take in the issues of how a person becomes a born again believer, what the church's purpose for existence is, and how the church is to pursue that purpose in its local setting. There will be no unity if these issues are not addressed and agreed upon. The reason a church can have unity with a lesser core than a marriage is simple: we don't have to live with each other 24 hours a day. Unity can exist with a lesser core if the demands of each day have a bit of space in the relationships. And, again, if the people seeking unity are only seeking to establish a fellowship of churches, the core can be even less demanding because the churches can have freedom to function individually with less demand for unity of practice since the goal is only for broad, and infrequent relational interaction. And, if the unity that is sought is simply a desire that the churches of an area come together for a common religious service on an infrequent basis, then the core can be even smaller in terms of what must be agreed upon beforehand.
So, what is the minimal core that makes religious unity possible? To answer that all we have to do is ask: what is the minimal core that distinguishes a believer from an unbeliever? Unfortunately we have run out of space. More in another article. (193)