When Constantine gathered people he perceived to be the leaders of Christianity together in Nicaea in the year 325, part of what he caused to occur was an entitlement of “ecumene” over the church. This description means literally “the whole inhabited world.” It is as much a mistake as calling the church of Rome “catholic,” which means literally “the universal” church.
Both terms are claims of genuineness and uniqueness that are inaccurate. The Roman church is not the entirety of the Church of Jesus, and the Ecumenical Movement is not the entirety of the Church of Jesus. There is an entire, universal church, and there is a unity in her parts – her members – that is borne from the fact that there is only one Body and one Spirit, however.
Fear of these false teachings has caused some to despise any talk of unity among believers who disagree on points of doctrine. “If we can’t agree on all things, you must be wrong” is one of their mottoes.
If we cannot find the path to unity among believers, we will not be part of the fulfillment of the wondrous prophetic picture of the Church described by Paul in Ephesians 4.
But we will. Even if it takes so much hardship and threat and persecution that we will hate the enemies of Jesus enough to begin to love His people enough to become His body and be built up in love by what every joint supplies. A joint is a relationship. The most genuine and powerful manifestation of the body of Christ yet seen in the earth will arise from the relationships that believers have with other believers through which mighty works will flow.